Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

Replacement is probably trivial; rename Mutex to OldMutex, rename CriticalSection to Mutex, recompile. But there are lots of mutexes in the system and these are potentially owned. Transforming unowned ones is trivial, but transforming owned ones is, I think, impossible. But at least in my system there are no owned mutexes or monitors.

Frank (or anyone else), would you be interested in creating a replacement for Squeak's Monitor based on CriticalSection?

Here are the two business methods: *CriticalSection methods for mutual exclusion* *critical:* aBlock "Evaluate aBlock protected by the receiver." ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

*critical:* aBlock *ifLocked:* lockedBlock "*Answer the evaluation of aBlock protected by the receiver. If it is already in a critical* * section on behalf of some other process answer the evaluation of lockedBlock.*" ^self primitiveTestAndSetOwnershipOfCriticalSection ifNil: [lockedBlock value] ifNotNil:[:alreadyOwner| alreadyOwner ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]]

and the primitives: *CriticalSection methods for private-primitives* *primitiveEnterCriticalSection* "Primitive. The receiver must be unowned or owned by the current process to proceed. Answer if the process is owned by the current process." <primitive: 186> self primitiveFailed "In the spirit of the following" "[owner ifNil: [owner := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. Processor activeProcess suspend] valueUnpreemptively"

*primitiveExitCriticalSection* "Primitive. Set te receiver to unowned and if any processes are waiting on the receiver then proceed the first one, indicating that the receiver is unowned." <primitive: 185> self primitiveFailed "In the spirit of the following" "[owner := nil. self isEmpty ifFalse: [process := self removeFirst. process resume]] valueUnpreemptively"

*primitiveTestAndSetOwnershipOfCriticalSection* "Primitive. Attempt to set the ownership of the receiver. If the receiver is unowned set its owningProcess to the activeProcess and answer false. If the receiver is owned by the activeProcess answer true. If the receiver is owned by some other process answer nil." <primitive: 187> self primitiveFail "In the spirit of the following" "[owner ifNil: [owningProcess := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively"

2016-01-07 13:24 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Hello.

I hear about new Monitor implementation based on new primitives. Where to get it?

_,,,^..^,,,_ best, Eliot

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

and here's a version with a better class comment

On Thu, Jan 7, 2016 at 9:12 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

This is great Eliot. Thank you and 3DICC. After loading the changeset into Pharo-50515 (32 bit Spur) I get the following results on my laptop i5-2520M @ 2.50GHz

#('Mutex -> 254,047 per second' 'Monitor -> 450,442 per second' 'CriticalSection -> 683,393 per second')

In a fresh Image "Mutex allInstances basicInspect" lists just two mutexes... 1. NetNameResolver-->ResolverMutex 2. ThreadSafeTranscript-->accessSemaphore

cheers -ben

...

Replacement is probably trivial; rename Mutex to OldMutex, rename CriticalSection to Mutex, recompile. But there are lots of mutexes in the system and these are potentially owned. Transforming unowned ones is trivial, but transforming owned ones is, I think, impossible. But at least in my system there are no owned mutexes or monitors.

Frank (or anyone else), would you be interested in creating a replacement for Squeak's Monitor based on CriticalSection?

Here are the two business methods: CriticalSection methods for mutual exclusion critical: aBlock "Evaluate aBlock protected by the receiver." ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

critical: aBlock ifLocked: lockedBlock "Answer the evaluation of aBlock protected by the receiver. If it is already in a critical section on behalf of some other process answer the evaluation of lockedBlock." ^self primitiveTestAndSetOwnershipOfCriticalSection ifNil: [lockedBlock value] ifNotNil:[:alreadyOwner| alreadyOwner ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]]

and the primitives: CriticalSection methods for private-primitives primitiveEnterCriticalSection "Primitive. The receiver must be unowned or owned by the current process to proceed. Answer if the process is owned by the current process." <primitive: 186> self primitiveFailed "In the spirit of the following" "[owner ifNil: [owner := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. Processor activeProcess suspend] valueUnpreemptively"

primitiveExitCriticalSection "Primitive. Set te receiver to unowned and if any processes are waiting on the receiver then proceed the first one, indicating that the receiver is unowned." <primitive: 185> self primitiveFailed "In the spirit of the following" "[owner := nil. self isEmpty ifFalse: [process := self removeFirst. process resume]] valueUnpreemptively"

primitiveTestAndSetOwnershipOfCriticalSection "Primitive. Attempt to set the ownership of the receiver. If the receiver is unowned set its owningProcess to the activeProcess and answer false. If the receiver is owned by the activeProcess answer true. If the receiver is owned by some other process answer nil." <primitive: 187> self primitiveFail "In the spirit of the following" "[owner ifNil: [owningProcess := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively"

...

2016-01-07 13:24 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Hello.

I hear about new Monitor implementation based on new primitives. Where to get it?

_,,,^..^,,,_ best, Eliot

-- _,,,^..^,,,_ best, Eliot

On Fri, Jan 8, 2016 at 2:51 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

Hi Ben,

On Thu, Jan 7, 2016 at 10:39 AM, Ben Coman btc@openinworld.com wrote:

...

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

and here's a version with a better class comment

On Thu, Jan 7, 2016 at 9:12 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

This is great Eliot. Thank you and 3DICC. After loading the changeset into Pharo-50515 (32 bit Spur) I get the following results on my laptop i5-2520M @ 2.50GHz

#('Mutex -> 254,047 per second' 'Monitor -> 450,442 per second' 'CriticalSection -> 683,393 per second')

In a fresh Image "Mutex allInstances basicInspect" lists just two mutexes...

1. NetNameResolver-->ResolverMutex
2. ThreadSafeTranscript-->accessSemaphore

I hate myself for getting distracted but I'm finding this is un. One can migrate to the new representation using normal Monticello loads by

In the first version redefine Mutex and Monitor to subclass LinkedList and have their owner/ownerProcess inst var first (actually third after firstLink & lastLink), and add the primitives.

In the next version check that all Mutex and Monitor instanes are unowned and then redefine to discard excess inst vars

Let me test this before committing, and see that all tests are ok.

Should Mutex and Monitor both directly subclass LinkedList and duplicate the primitives in each?

Or should they both subclass CriticalSection which subclasses LinkedList so the primitives are only defined once?

What effect would using the primitives from the superclass have on performance? If any, I'd vote to optimise for duplication rather than "nice" design, but our comments should document this.

cheers -ben

Now I implement pragma approach to set up local variable during termination process. So I can write such methods:

critical: aBlock "Evaluate aBlock protected by the receiver." | lockAcquired | <lockAt: #lock trackStateAt: 1> lockAcquired := false. ^[ lockAcquired := true. lockAcquired := lock wait. aBlock value ] ensure: [lockAcquired ifTrue: [lock signal]].

And Process>>terminate detects waiting on such methods and push false to variable lockAcquired (which is 1 temp here). This approach allow me to use multiple "locks" (semaphores or whatever) in single method which I need for ReadWriteLock.

2016-01-08 18:31 GMT+01:00 Eliot Miranda eliot.miranda@gmail.com:

Hi Ben,

On Thu, Jan 7, 2016 at 4:40 PM, Ben Coman btc@openinworld.com wrote:

...

On Fri, Jan 8, 2016 at 2:51 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

Hi Ben,

On Thu, Jan 7, 2016 at 10:39 AM, Ben Coman btc@openinworld.com wrote:

...

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda <eliot.miranda@gmail.com

...

wrote:

...

and here's a version with a better class comment

On Thu, Jan 7, 2016 at 9:12 AM, Eliot Miranda <

eliot.miranda@gmail.com>

...

...

...

wrote:

...

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera <

bera.clement@gmail.com>

...

...

...

...

wrote: > > Hello, > > Eliot, please, you told me you had the code and Denis is

interested.

...

...

...

...

> > It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a

fairly raw

...

...

...

...

state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is

quicker

...

...

...

...

because it uses three new primitives to manage entering a critical

section

...

...

...

...

and setting the owner, exiting the critical section and releasing

the owner,

...

...

...

...

and testing if a critical section, entering if the section is

unowned. The

...

...

...

...

use of the primitives means fewer block activations and ensure:

blocks in

...

...

...

...

entering and exiting the critical section, and that's the actual

cause of

...

...

...

...

the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical:

[n

...

...

...

...

:= n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical:

[n

...

...

...

...

:= n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical:

[n

...

...

...

...

:= n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical:

[n

...

...

...

...

:= n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

This is great Eliot. Thank you and 3DICC. After loading the changeset into Pharo-50515 (32 bit Spur) I get the following results on my laptop i5-2520M @ 2.50GHz

#('Mutex -> 254,047 per second' 'Monitor -> 450,442 per second' 'CriticalSection -> 683,393 per second')

In a fresh Image "Mutex allInstances basicInspect" lists just two mutexes...

1. NetNameResolver-->ResolverMutex
2. ThreadSafeTranscript-->accessSemaphore

I hate myself for getting distracted but I'm finding this is un. One

can

...

migrate to the new representation using normal Monticello loads by

In the first version redefine Mutex and Monitor to subclass LinkedList

and

...

have their owner/ownerProcess inst var first (actually third after

firstLink

...

& lastLink), and add the primitives.

In the next version check that all Mutex and Monitor instanes are

unowned

...

and then redefine to discard excess inst vars

Let me test this before committing, and see that all tests are ok.

Should Mutex and Monitor both directly subclass LinkedList and duplicate the primitives in each?

Or should they both subclass CriticalSection which subclasses LinkedList so the primitives are only defined once?

That's a good idea. Feel free to change the code, but test that the Monticello load handles this case properly first :-). Actually, given that the default state of all the Mutex and Monitor instances in the image is unowned (owner process is nil) then it'll just work anyway. If we do that, we must make sure to include the ICC copyright in CriticalSection's class comment, and can eliminate it from the primitives.

What effect would using the primitives from the superclass have on

...

performance? If any, I'd vote to optimise for duplication rather than "nice" design, but our comments should document this.

Likely in the noise. The inline cacheing machinery in the VM is far cheaper than the real overheads here which are in block creation, process switch, interpreter primitive invocation.

...

cheers -ben

-- _,,,^..^,,,_ best, Eliot

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because: 1. Concurrency bugs can be subtle and the *exact* conditions can be hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

4. Its faster (for me, the least argument given that.

btw, Looking at the following... CriticalSection>>critical: aBlock ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

without intimate VM knowledge but seeing Eliot recently say "invocations of methods with primitives [...] are not suspension points, unless their primitives fail" -- I'm paranoid that since #ensure: primitive 198 always fail, there might be some some small window for a race where a process might be terminated before #primitiveExitCriticalSection can be executed. I'll take a refutation of this to improve the method comment.

The following instils more confidence...

CriticalSection2>>critical: aBlock | reEntered | reEntered := false. [ reEntered := self primitiveEnterCriticalSection. aBlock value ] ensure: [ reEntered ifFalse: [ self primitiveExitCriticalSection] ]

but performance is reduced... "#('Mutex -> 282,511 per second' 'Monitor -> 479,217 per second' 'CriticalSection -> 729,049 per second' 'CriticalSection2 -> 571,631 per second')"

Then again, any termination from within a critical section is anyhow problematic since potentially data structures are left in a indeterminate state.

[1] http://forum.world.st/Super-fast-delay-td4787257.html [2] https://pharo.fogbugz.com/default.asp?13755 [3] https://git.io/vuDnA

cheers -ben

Stef

Hi Ben,

On Thu, Jan 7, 2016 at 10:39 AM, Ben Coman btc@openinworld.comwrote:

...

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

and here's a version with a better class comment

On Thu, Jan 7, 2016 at 9:12 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

This is great Eliot. Thank you and 3DICC. After loading the changeset into Pharo-50515 (32 bit Spur) I get the following results on my laptop i5-2520M @ 2.50GHz

#('Mutex -> 254,047 per second' 'Monitor -> 450,442 per second' 'CriticalSection -> 683,393 per second')

In a fresh Image "Mutex allInstances basicInspect" lists just two mutexes...

1. NetNameResolver-->ResolverMutex
2. ThreadSafeTranscript-->accessSemaphore

I hate myself for getting distracted but I'm finding this is un. One can migrate to the new representation using normal Monticello loads by

In the first version redefine Mutex and Monitor to subclass LinkedList and have their owner/ownerProcess inst var first (actually third after firstLink & lastLink), and add the primitives.

In the next version check that all Mutex and Monitor instanes are unowned and then redefine to discard excess inst vars

Let me test this before committing, and see that all tests are ok.

...

cheers -ben

...

...

Replacement is probably trivial; rename Mutex to OldMutex, rename CriticalSection to Mutex, recompile. But there are lots of mutexes in the system and these are potentially owned. Transforming unowned ones is trivial, but transforming owned ones is, I think, impossible. But at least in my system there are no owned mutexes or monitors.

Frank (or anyone else), would you be interested in creating a replacement for Squeak's Monitor based on CriticalSection?

Here are the two business methods: CriticalSection methods for mutual exclusion critical: aBlock "Evaluate aBlock protected by the receiver." ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

critical: aBlock ifLocked: lockedBlock "Answer the evaluation of aBlock protected by the receiver. If it is already in a critical section on behalf of some other process answer the evaluation of lockedBlock." ^self primitiveTestAndSetOwnershipOfCriticalSection ifNil: [lockedBlock value] ifNotNil:[:alreadyOwner| alreadyOwner ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]]

and the primitives: CriticalSection methods for private-primitives primitiveEnterCriticalSection "Primitive. The receiver must be unowned or owned by the current process to proceed. Answer if the process is owned by the current process." <primitive: 186> self primitiveFailed "In the spirit of the following" "[owner ifNil: [owner := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. Processor activeProcess suspend] valueUnpreemptively"

primitiveExitCriticalSection "Primitive. Set te receiver to unowned and if any processes are waiting on the receiver then proceed the first one, indicating that the receiver is unowned." <primitive: 185> self primitiveFailed "In the spirit of the following" "[owner := nil. self isEmpty ifFalse: [process := self removeFirst. process resume]] valueUnpreemptively"

primitiveTestAndSetOwnershipOfCriticalSection "Primitive. Attempt to set the ownership of the receiver. If the receiver is unowned set its owningProcess to the activeProcess and answer false. If the receiver is owned by the activeProcess answer true. If the receiver is owned by some other process answer nil." <primitive: 187> self primitiveFail "In the spirit of the following" "[owner ifNil: [owningProcess := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively"

...

2016-01-07 13:24 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Hello.

I hear about new Monitor implementation based on new primitives. Where to get it?

On Fri, Jan 8, 2016 at 9:39 PM, Ben Coman btc@openinworld.com wrote:

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

...

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because:

1. Concurrency bugs can be subtle and the *exact* conditions can be

hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually

consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes

around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

Points 2 & 3 might possibly be addressed by having new primitiveWaitReturned *always* return true, so if the process is terminated while waiting, the assignment to signalConsumed doesn't occur...

critical: mutuallyExcludedBlock signalConsumed := false. [ signalConsumed := self primitiveWaitReturned. blockValue := mutuallyExcludedBlock value ] ensure: [ signalConsumed ifTrue: [self signal] ]. ^blockValue

where primitiveWait (https://git.io/vuDjd) is copied and (just guessing) the marked line added...

primitiveWaitReturned | sema excessSignals activeProc inInterpreter | sema := self stackTop. "rcvr" "==>>" self pop: argumentCount + 1 thenPush: objectMemory trueObject. "<<==" excessSignals := self fetchInteger: ExcessSignalsIndex ofObject: sema. excessSignals > 0 ifTrue: [self storeInteger: ExcessSignalsIndex ofObject: sema withValue: excessSignals - 1] ifFalse: inInterpreter := instructionPointer >= objectMemory startOfMemory. activeProc := self activeProcess. self addLastLink: activeProc toList: sema. self transferTo: self wakeHighestPriority from: CSWait. self forProcessPrimitiveReturnToExecutivePostContextSwitch: inInterpreter]

which I guess could be added quickly if Esteban could compile the latest pharo-spur-vm ;)

cheers -ben

4. Its faster

btw, Looking at the following... CriticalSection>>critical: aBlock ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

without intimate VM knowledge but seeing Eliot recently say "invocations of methods with primitives [...] are not suspension points, unless their primitives fail" -- I'm paranoid that since #ensure: primitive 198 always fail, there might be some some small window for a race where a process might be terminated before #primitiveExitCriticalSection can be executed. I'll take a refutation of this to improve the method comment.

The following instils more confidence...

CriticalSection2>>critical: aBlock | reEntered | reEntered := false. [ reEntered := self primitiveEnterCriticalSection. aBlock value ] ensure: [ reEntered ifFalse: [ self primitiveExitCriticalSection] ]

but performance is reduced... "#('Mutex -> 282,511 per second' 'Monitor -> 479,217 per second' 'CriticalSection -> 729,049 per second' 'CriticalSection2 -> 571,631 per second')"

Then again, any termination from within a critical section is anyhow problematic since potentially data structures are left in a indeterminate state.

[1] http://forum.world.st/Super-fast-delay-td4787257.html [2] https://pharo.fogbugz.com/default.asp?13755 [3] https://git.io/vuDnA

cheers -ben

...

Stef

Hi Ben,

On Thu, Jan 7, 2016 at 10:39 AM, Ben Coman btc@openinworld.comwrote:

...

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

and here's a version with a better class comment

On Thu, Jan 7, 2016 at 9:12 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

This is great Eliot. Thank you and 3DICC. After loading the changeset into Pharo-50515 (32 bit Spur) I get the following results on my laptop i5-2520M @ 2.50GHz

#('Mutex -> 254,047 per second' 'Monitor -> 450,442 per second' 'CriticalSection -> 683,393 per second')

In a fresh Image "Mutex allInstances basicInspect" lists just two mutexes...

1. NetNameResolver-->ResolverMutex
2. ThreadSafeTranscript-->accessSemaphore

I hate myself for getting distracted but I'm finding this is un. One can migrate to the new representation using normal Monticello loads by

In the first version redefine Mutex and Monitor to subclass LinkedList and have their owner/ownerProcess inst var first (actually third after firstLink & lastLink), and add the primitives.

In the next version check that all Mutex and Monitor instanes are unowned and then redefine to discard excess inst vars

Let me test this before committing, and see that all tests are ok.

...

cheers -ben

...

...

Replacement is probably trivial; rename Mutex to OldMutex, rename CriticalSection to Mutex, recompile. But there are lots of mutexes in the system and these are potentially owned. Transforming unowned ones is trivial, but transforming owned ones is, I think, impossible. But at least in my system there are no owned mutexes or monitors.

Frank (or anyone else), would you be interested in creating a replacement for Squeak's Monitor based on CriticalSection?

Here are the two business methods: CriticalSection methods for mutual exclusion critical: aBlock "Evaluate aBlock protected by the receiver." ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

critical: aBlock ifLocked: lockedBlock "Answer the evaluation of aBlock protected by the receiver. If it is already in a critical section on behalf of some other process answer the evaluation of lockedBlock." ^self primitiveTestAndSetOwnershipOfCriticalSection ifNil: [lockedBlock value] ifNotNil:[:alreadyOwner| alreadyOwner ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]]

and the primitives: CriticalSection methods for private-primitives primitiveEnterCriticalSection "Primitive. The receiver must be unowned or owned by the current process to proceed. Answer if the process is owned by the current process." <primitive: 186> self primitiveFailed "In the spirit of the following" "[owner ifNil: [owner := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. Processor activeProcess suspend] valueUnpreemptively"

primitiveExitCriticalSection "Primitive. Set te receiver to unowned and if any processes are waiting on the receiver then proceed the first one, indicating that the receiver is unowned." <primitive: 185> self primitiveFailed "In the spirit of the following" "[owner := nil. self isEmpty ifFalse: [process := self removeFirst. process resume]] valueUnpreemptively"

primitiveTestAndSetOwnershipOfCriticalSection "Primitive. Attempt to set the ownership of the receiver. If the receiver is unowned set its owningProcess to the activeProcess and answer false. If the receiver is owned by the activeProcess answer true. If the receiver is owned by some other process answer nil." <primitive: 187> self primitiveFail "In the spirit of the following" "[owner ifNil: [owningProcess := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively"

...

2016-01-07 13:24 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com: > > > Hello. > > I hear about new Monitor implementation based on new primitives. > Where to get it?

On 08 Jan 2016, at 4:25 , Ben Coman btc@openInWorld.com wrote:

On Fri, Jan 8, 2016 at 9:39 PM, Ben Coman <btc@openinworld.com mailto:btc@openinworld.com> wrote:

...

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

...

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because:

1. Concurrency bugs can be subtle and the *exact* conditions can be

hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually

consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes

around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

Points 2 & 3 might possibly be addressed by having new primitiveWaitReturned *always* return true, so if the process is terminated while waiting, the assignment to signalConsumed doesn't occur...

critical: mutuallyExcludedBlock signalConsumed := false. [ signalConsumed := self primitiveWaitReturned. blockValue := mutuallyExcludedBlock value ] ensure: [ signalConsumed ifTrue: [self signal] ]. ^blockValue

where primitiveWait (https://git.io/vuDjd https://git.io/vuDjd) is copied and (just guessing) the marked line added...

primitiveWaitReturned | sema excessSignals activeProc inInterpreter | sema := self stackTop. "rcvr" "==>>" self pop: argumentCount + 1 thenPush: objectMemory trueObject. "<<==" excessSignals := self fetchInteger: ExcessSignalsIndex ofObject: sema. excessSignals > 0 ifTrue: [self storeInteger: ExcessSignalsIndex ofObject: sema withValue: excessSignals - 1] ifFalse: inInterpreter := instructionPointer >= objectMemory startOfMemory. activeProc := self activeProcess. self addLastLink: activeProc toList: sema. self transferTo: self wakeHighestPriority from: CSWait. self forProcessPrimitiveReturnToExecutivePostContextSwitch: inInterpreter]

which I guess could be added quickly if Esteban could compile the latest pharo-spur-vm ;)

cheers -ben

Won't work, there's no guarantee thread has actually ran and signalConsumed been assigned the primitive result after Semaphore resumed the waiting thread, before a higher priority thread runs and terminates it. (which is exactly the case handled by special code in #terminate)

Cheers, Henry

Eliot I found that there are no methods for simulation code (if it right name for it). So stepping over new primitives failed (which is infinite recursion for Pharo case)

Context>>doPrimitive: primitiveIndex method: meth receiver: aReceiver args: arguments ... "Mutex>>primitiveEnterCriticalSection Mutex>>primitiveTestAndSetOwnershipOfCriticalSection" (primitiveIndex = 186 or: [primitiveIndex = 187]) ifTrue: [| active effective | active := Processor activeProcess. effective := active effectiveProcess. "active == effective" value := primitiveIndex = 186 ifTrue: [aReceiver *primitiveEnterCriticalSectionOnBehalfOf*: effective] ifFalse: [aReceiver *primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf*: effective]. ^(self isPrimFailToken: value) ifTrue: [value] ifFalse: [self push: value]].

How this methods should be implemented?

2016-01-11 13:59 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

Hello. I publish slice 17373 https://pharo.fogbugz.com/f/cases/17373/Mutex-should-be-based-on-VM-primitives-and-implement-critical-methods-from-Semaphore .

I introduce LockOwnership class which implements VM primitives as:

• acquire
• tryAcquire
• release

(It comment saves copyright from CriticalSection)

Mutext uses it as ownership instance variable to implement critical methods correctly:

• critical:
• critical:ifLocked:
• critical:ifError:
• critical:ifCurtailed:

For the integration process old Mutex instance variables are not removed. So loading this code should not broke current Mutex instances. But when we integrate it Mutex will have only variable ownership.

If you look critical implementation you will understand why I not like semantic of primitives. it should be inverted in future. #acquire should return true when ownership is acquired right now.

Process>>terminate now detects waiting on LockOwnership and ask it to handle wait termination.Then LockOwnership inject right value into lock state variable. Such variables should be marked with special pragma <lockAt: #ownershipVariableName tracksStateAt: 1> "index of local variable" Method can contain mulpible pragmas to reference all ownerships in method. ReadWriteLock for example needs this.

2016-01-11 13:30 GMT+01:00 Henrik Johansen henrik.s.johansen@veloxit.no:

...

On 08 Jan 2016, at 4:25 , Ben Coman <btc@openInWorld.com btc@openinworld.com> wrote:

On Fri, Jan 8, 2016 at 9:39 PM, Ben Coman btc@openinworld.com wrote:

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because:

1. Concurrency bugs can be subtle and the *exact* conditions can be

hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually

consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes

around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

Points 2 & 3 might possibly be addressed by having new primitiveWaitReturned *always* return true, so if the process is terminated while waiting, the assignment to signalConsumed doesn't occur...

critical: mutuallyExcludedBlock signalConsumed := false. [ signalConsumed := self primitiveWaitReturned. blockValue := mutuallyExcludedBlock value ] ensure: [ signalConsumed ifTrue: [self signal] ]. ^blockValue

where primitiveWait (https://git.io/vuDjd) is copied and (just guessing) the marked line added...

primitiveWaitReturned | sema excessSignals activeProc inInterpreter | sema := self stackTop. "rcvr" "==>>" self pop: argumentCount + 1 thenPush: objectMemory trueObject. "<<==" excessSignals := self fetchInteger: ExcessSignalsIndex ofObject: sema. excessSignals > 0 ifTrue: [self storeInteger: ExcessSignalsIndex ofObject: sema withValue: excessSignals - 1] ifFalse: inInterpreter := instructionPointer >= objectMemory startOfMemory. activeProc := self activeProcess. self addLastLink: activeProc toList: sema. self transferTo: self wakeHighestPriority from: CSWait. self forProcessPrimitiveReturnToExecutivePostContextSwitch: inInterpreter]

which I guess could be added quickly if Esteban could compile the latest pharo-spur-vm ;)

cheers -ben

Won't work, there's no guarantee thread has actually ran and signalConsumed been assigned the primitive result after Semaphore resumed the waiting thread, before a higher priority thread runs and terminates it. (which is exactly the case handled by special code in #terminate)

Cheers, Henry

Thanks Denis,

On Mon, Jan 11, 2016 at 6:54 AM, Denis Kudriashov dionisiydk@gmail.com wrote:

I write it such way:

primitiveEnterCriticalSectionOnBehalfOf: activeProcess [owningProcess ifNil: [owningProcess := activeProcess. ^false]. owningProcess = activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. activeProcess suspend] valueUnpreemptively

primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf: activeProcess [owningProcess ifNil: [owningProcess := activeProcess. ^false]. owningProcess = activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively

This looks good. Do you have methods you've written? I'd like to use yours as they have your time stamp.

2016-01-11 14:58 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Eliot I found that there are no methods for simulation code (if it right name for it). So stepping over new primitives failed (which is infinite recursion for Pharo case)

Context>>doPrimitive: primitiveIndex method: meth receiver: aReceiver args: arguments ... "Mutex>>primitiveEnterCriticalSection Mutex>>primitiveTestAndSetOwnershipOfCriticalSection" (primitiveIndex = 186 or: [primitiveIndex = 187]) ifTrue: [| active effective | active := Processor activeProcess. effective := active effectiveProcess. "active == effective" value := primitiveIndex = 186 ifTrue: [aReceiver *primitiveEnterCriticalSectionOnBehalfOf*: effective] ifFalse: [aReceiver *primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf*: effective]. ^(self isPrimFailToken: value) ifTrue: [value] ifFalse: [self push: value]].

How this methods should be implemented?

2016-01-11 13:59 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Hello. I publish slice 17373 https://pharo.fogbugz.com/f/cases/17373/Mutex-should-be-based-on-VM-primitives-and-implement-critical-methods-from-Semaphore .

I introduce LockOwnership class which implements VM primitives as:

• acquire
• tryAcquire
• release

(It comment saves copyright from CriticalSection)

Mutext uses it as ownership instance variable to implement critical methods correctly:

• critical:
• critical:ifLocked:
• critical:ifError:
• critical:ifCurtailed:

For the integration process old Mutex instance variables are not removed. So loading this code should not broke current Mutex instances. But when we integrate it Mutex will have only variable ownership.

If you look critical implementation you will understand why I not like semantic of primitives. it should be inverted in future. #acquire should return true when ownership is acquired right now.

Process>>terminate now detects waiting on LockOwnership and ask it to handle wait termination.Then LockOwnership inject right value into lock state variable. Such variables should be marked with special pragma <lockAt: #ownershipVariableName tracksStateAt: 1> "index of local variable" Method can contain mulpible pragmas to reference all ownerships in method. ReadWriteLock for example needs this.

2016-01-11 13:30 GMT+01:00 Henrik Johansen <henrik.s.johansen@veloxit.no

...

:

...

On 08 Jan 2016, at 4:25 , Ben Coman <btc@openInWorld.com btc@openinworld.com> wrote:

On Fri, Jan 8, 2016 at 9:39 PM, Ben Coman btc@openinworld.com wrote:

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because:

1. Concurrency bugs can be subtle and the *exact* conditions can be

hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually

consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes

around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

Points 2 & 3 might possibly be addressed by having new primitiveWaitReturned *always* return true, so if the process is terminated while waiting, the assignment to signalConsumed doesn't occur...

critical: mutuallyExcludedBlock signalConsumed := false. [ signalConsumed := self primitiveWaitReturned. blockValue := mutuallyExcludedBlock value ] ensure: [ signalConsumed ifTrue: [self signal] ]. ^blockValue

where primitiveWait (https://git.io/vuDjd) is copied and (just guessing) the marked line added...

primitiveWaitReturned | sema excessSignals activeProc inInterpreter | sema := self stackTop. "rcvr" "==>>" self pop: argumentCount + 1 thenPush: objectMemory trueObject. "<<==" excessSignals := self fetchInteger: ExcessSignalsIndex ofObject: sema. excessSignals > 0 ifTrue: [self storeInteger: ExcessSignalsIndex ofObject: sema withValue: excessSignals - 1] ifFalse: inInterpreter := instructionPointer >= objectMemory startOfMemory. activeProc := self activeProcess. self addLastLink: activeProc toList: sema. self transferTo: self wakeHighestPriority from: CSWait. self forProcessPrimitiveReturnToExecutivePostContextSwitch: inInterpreter]

which I guess could be added quickly if Esteban could compile the latest pharo-spur-vm ;)

cheers -ben

Won't work, there's no guarantee thread has actually ran and signalConsumed been assigned the primitive result after Semaphore resumed the waiting thread, before a higher priority thread runs and terminates it. (which is exactly the case handled by special code in #terminate)

Cheers, Henry

2016-01-11 14:58 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Eliot I found that there are no methods for simulation code (if it right name for it). So stepping over new primitives failed (which is infinite recursion for Pharo case)

Context>>doPrimitive: primitiveIndex method: meth receiver: aReceiver args: arguments ... "Mutex>>primitiveEnterCriticalSection Mutex>>primitiveTestAndSetOwnershipOfCriticalSection" (primitiveIndex = 186 or: [primitiveIndex = 187]) ifTrue: [| active effective | active := Processor activeProcess. effective := active effectiveProcess. "active == effective" value := primitiveIndex = 186 ifTrue: [aReceiver primitiveEnterCriticalSectionOnBehalfOf: effective] ifFalse: [aReceiver primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf: effective]. ^(self isPrimFailToken: value) ifTrue: [value] ifFalse: [self push: value]].

How this methods should be implemented?

On Mon, Jan 11, 2016 at 10:54 PM, Denis Kudriashov dionisiydk@gmail.com wrote:

I write it such way:

primitiveEnterCriticalSectionOnBehalfOf: activeProcess [owningProcess ifNil: [owningProcess := activeProcess. ^false]. owningProcess = activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. activeProcess suspend] valueUnpreemptively

primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf: activeProcess [owningProcess ifNil: [owningProcess := activeProcess. ^false]. owningProcess = activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively

@Dennis, Why not... primitiveEnterCriticalSectionOnBehalfOf: activeProcess <primitive: 186> self primitiveFailed

I had been meaning to ask what this code at the top of the primitive was for... argumentCount > 0 ifTrue: [criticalSection := self stackValue: 1. "rcvr" activeProc := self stackTop] ifFalse: [criticalSection := self stackTop. "rcvr" activeProc := self activeProcess].

but took a wild guess its to support onBehalfOf type calls. So I tried...

| cs p1 p2 p3 | cs := CriticalSection new. p1 := [ cs critical: [ Transcript crShow: 1 ] ] newProcess priority: 41. p2 := [ cs critical: [ Transcript crShow: 2 ] ] newProcess priority: 41. p3 := [ cs critical: [ Transcript crShow: 3 ] ] newProcess priority: 41. cs primitiveEnterCriticalSectionOnBehalfOf: p3. p1 resume. p2 resume. p3 resume. cs primitiveExitCriticalSection.

and indeed the result is... 3 1 2

cheers -ben

On Mon, Jan 11, 2016 at 9:58 PM, Denis Kudriashov dionisiydk@gmail.com wrote:

Eliot I found that there are no methods for simulation code (if it right name for it). So stepping over new primitives failed (which is infinite recursion for Pharo case)

Context>>doPrimitive: primitiveIndex method: meth receiver: aReceiver args: arguments ... "Mutex>>primitiveEnterCriticalSection Mutex>>primitiveTestAndSetOwnershipOfCriticalSection" (primitiveIndex = 186 or: [primitiveIndex = 187]) ifTrue: [| active effective | active := Processor activeProcess. effective := active effectiveProcess. "active == effective" value := primitiveIndex = 186 ifTrue: [aReceiver primitiveEnterCriticalSectionOnBehalfOf: effective] ifFalse: [aReceiver primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf: effective]. ^(self isPrimFailToken: value) ifTrue: [value] ifFalse: [self push: value]].

How this methods should be implemented?

2016-01-11 13:59 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Hello. I publish slice 17373.

I introduce LockOwnership class which implements VM primitives as:

• acquire
• tryAcquire
• release

(It comment saves copyright from CriticalSection)

I don't think that is proper. The code is the same, just some names have changed. I'll bet the primitives were funded by 3DICC too, so credit where credit is due. cheers -ben

Hi Denis,

On Mon, Jan 11, 2016 at 5:58 AM, Denis Kudriashov dionisiydk@gmail.com wrote:

Eliot I found that there are no methods for simulation code (if it right name for it). So stepping over new primitives failed (which is infinite recursion for Pharo case)

Find the Squeak code attached. Merge it with the Pharo code (renaming ContextPart to COntext of course; something we'll do in Squeak eventually :-) )..

Context>>doPrimitive: primitiveIndex method: meth receiver: aReceiver args: arguments ... "Mutex>>primitiveEnterCriticalSection Mutex>>primitiveTestAndSetOwnershipOfCriticalSection" (primitiveIndex = 186 or: [primitiveIndex = 187]) ifTrue: [| active effective | active := Processor activeProcess. effective := active effectiveProcess. "active == effective" value := primitiveIndex = 186 ifTrue: [aReceiver *primitiveEnterCriticalSectionOnBehalfOf*: effective] ifFalse: [aReceiver *primitiveTestAndSetOwnershipOfCriticalSectionOnBehalfOf*: effective]. ^(self isPrimFailToken: value) ifTrue: [value] ifFalse: [self push: value]].

How this methods should be implemented?

2016-01-11 13:59 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com:

...

Hello. I publish slice 17373 https://pharo.fogbugz.com/f/cases/17373/Mutex-should-be-based-on-VM-primitives-and-implement-critical-methods-from-Semaphore .

I introduce LockOwnership class which implements VM primitives as:

• acquire
• tryAcquire
• release

(It comment saves copyright from CriticalSection)

Mutext uses it as ownership instance variable to implement critical methods correctly:

• critical:
• critical:ifLocked:
• critical:ifError:
• critical:ifCurtailed:

For the integration process old Mutex instance variables are not removed. So loading this code should not broke current Mutex instances. But when we integrate it Mutex will have only variable ownership.

If you look critical implementation you will understand why I not like semantic of primitives. it should be inverted in future. #acquire should return true when ownership is acquired right now.

Process>>terminate now detects waiting on LockOwnership and ask it to handle wait termination.Then LockOwnership inject right value into lock state variable. Such variables should be marked with special pragma <lockAt: #ownershipVariableName tracksStateAt: 1> "index of local variable" Method can contain mulpible pragmas to reference all ownerships in method. ReadWriteLock for example needs this.

2016-01-11 13:30 GMT+01:00 Henrik Johansen henrik.s.johansen@veloxit.no :

...

On 08 Jan 2016, at 4:25 , Ben Coman <btc@openInWorld.com btc@openinworld.com> wrote:

On Fri, Jan 8, 2016 at 9:39 PM, Ben Coman btc@openinworld.com wrote:

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because:

1. Concurrency bugs can be subtle and the *exact* conditions can be

hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually

consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes

around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

Points 2 & 3 might possibly be addressed by having new primitiveWaitReturned *always* return true, so if the process is terminated while waiting, the assignment to signalConsumed doesn't occur...

critical: mutuallyExcludedBlock signalConsumed := false. [ signalConsumed := self primitiveWaitReturned. blockValue := mutuallyExcludedBlock value ] ensure: [ signalConsumed ifTrue: [self signal] ]. ^blockValue

where primitiveWait (https://git.io/vuDjd) is copied and (just guessing) the marked line added...

primitiveWaitReturned | sema excessSignals activeProc inInterpreter | sema := self stackTop. "rcvr" "==>>" self pop: argumentCount + 1 thenPush: objectMemory trueObject. "<<==" excessSignals := self fetchInteger: ExcessSignalsIndex ofObject: sema. excessSignals > 0 ifTrue: [self storeInteger: ExcessSignalsIndex ofObject: sema withValue: excessSignals - 1] ifFalse: inInterpreter := instructionPointer >= objectMemory startOfMemory. activeProc := self activeProcess. self addLastLink: activeProc toList: sema. self transferTo: self wakeHighestPriority from: CSWait. self forProcessPrimitiveReturnToExecutivePostContextSwitch: inInterpreter]

which I guess could be added quickly if Esteban could compile the latest pharo-spur-vm ;)

cheers -ben

Won't work, there's no guarantee thread has actually ran and signalConsumed been assigned the primitive result after Semaphore resumed the waiting thread, before a higher priority thread runs and terminates it. (which is exactly the case handled by special code in #terminate)

Cheers, Henry

_,,,^..^,,,_ best, Eliot

Hi ben

thanks for your comments. I feel better.

Stef

On 08 Jan 2016, at 14:39, Ben Coman btc@openinworld.com wrote:

On Fri, Jan 8, 2016 at 5:42 PM, stephane ducasse stephane.ducasse@gmail.com wrote:

...

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Because:

1. Concurrency bugs can be subtle and the *exact* conditions can be

hard to reproduce for debugging. For example, the solution to a couple of problems with Delay [1] [2] were solved by moving away from Semaphore>>critical: to use signalling.

2. The in-image atomicity of determining whether a signal was actually

consumed or not during process suspension/termination is awkward. Its seems hard to *really* know for sure it right (but I haven't looked in depth into Denis' latest proposals.)

3. The existing in-image implementation of Semaphore>>critical messes

around in Process>>terminate in a *special* way that is not easy for those 100 eyes to understand. For example, I personally am not comfortable with understanding how the special Semaphore handling in Process>>terminate works, but I can easily follow how primitiveEnterCriticalSection just looking at the code [3].

4. Its faster (for me, the least argument given that.

btw, Looking at the following... CriticalSection>>critical: aBlock ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

without intimate VM knowledge but seeing Eliot recently say "invocations of methods with primitives [...] are not suspension points, unless their primitives fail" -- I'm paranoid that since #ensure: primitive 198 always fail, there might be some some small window for a race where a process might be terminated before #primitiveExitCriticalSection can be executed. I'll take a refutation of this to improve the method comment.

The following instils more confidence...

CriticalSection2>>critical: aBlock | reEntered | reEntered := false. [ reEntered := self primitiveEnterCriticalSection. aBlock value ] ensure: [ reEntered ifFalse: [ self primitiveExitCriticalSection] ]

but performance is reduced... "#('Mutex -> 282,511 per second' 'Monitor -> 479,217 per second' 'CriticalSection -> 729,049 per second' 'CriticalSection2 -> 571,631 per second')"

Then again, any termination from within a critical section is anyhow problematic since potentially data structures are left in a indeterminate state.

[1] http://forum.world.st/Super-fast-delay-td4787257.html [2] https://pharo.fogbugz.com/default.asp?13755 [3] https://git.io/vuDnA

cheers -ben

...

Stef

Hi Ben,

On Thu, Jan 7, 2016 at 10:39 AM, Ben Coman btc@openinworld.comwrote:

...

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

and here's a version with a better class comment

On Thu, Jan 7, 2016 at 9:12 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

This is great Eliot. Thank you and 3DICC. After loading the changeset into Pharo-50515 (32 bit Spur) I get the following results on my laptop i5-2520M @ 2.50GHz

#('Mutex -> 254,047 per second' 'Monitor -> 450,442 per second' 'CriticalSection -> 683,393 per second')

In a fresh Image "Mutex allInstances basicInspect" lists just two mutexes...

1. NetNameResolver-->ResolverMutex
2. ThreadSafeTranscript-->accessSemaphore

I hate myself for getting distracted but I'm finding this is un. One can migrate to the new representation using normal Monticello loads by

In the first version redefine Mutex and Monitor to subclass LinkedList and have their owner/ownerProcess inst var first (actually third after firstLink & lastLink), and add the primitives.

In the next version check that all Mutex and Monitor instanes are unowned and then redefine to discard excess inst vars

Let me test this before committing, and see that all tests are ok.

...

cheers -ben

...

...

Replacement is probably trivial; rename Mutex to OldMutex, rename CriticalSection to Mutex, recompile. But there are lots of mutexes in the system and these are potentially owned. Transforming unowned ones is trivial, but transforming owned ones is, I think, impossible. But at least in my system there are no owned mutexes or monitors.

Frank (or anyone else), would you be interested in creating a replacement for Squeak's Monitor based on CriticalSection?

Here are the two business methods: CriticalSection methods for mutual exclusion critical: aBlock "Evaluate aBlock protected by the receiver." ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

critical: aBlock ifLocked: lockedBlock "Answer the evaluation of aBlock protected by the receiver. If it is already in a critical section on behalf of some other process answer the evaluation of lockedBlock." ^self primitiveTestAndSetOwnershipOfCriticalSection ifNil: [lockedBlock value] ifNotNil:[:alreadyOwner| alreadyOwner ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]]

and the primitives: CriticalSection methods for private-primitives primitiveEnterCriticalSection "Primitive. The receiver must be unowned or owned by the current process to proceed. Answer if the process is owned by the current process." <primitive: 186> self primitiveFailed "In the spirit of the following" "[owner ifNil: [owner := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. self addLast: Processor activeProcess. Processor activeProcess suspend] valueUnpreemptively"

primitiveExitCriticalSection "Primitive. Set te receiver to unowned and if any processes are waiting on the receiver then proceed the first one, indicating that the receiver is unowned." <primitive: 185> self primitiveFailed "In the spirit of the following" "[owner := nil. self isEmpty ifFalse: [process := self removeFirst. process resume]] valueUnpreemptively"

primitiveTestAndSetOwnershipOfCriticalSection "Primitive. Attempt to set the ownership of the receiver. If the receiver is unowned set its owningProcess to the activeProcess and answer false. If the receiver is owned by the activeProcess answer true. If the receiver is owned by some other process answer nil." <primitive: 187> self primitiveFail "In the spirit of the following" "[owner ifNil: [owningProcess := Processor activeProcess. ^false]. owner = Processor activeProcess ifTrue: [^true]. ^nil] valueUnpreemptively"

...

2016-01-07 13:24 GMT+01:00 Denis Kudriashov dionisiydk@gmail.com: > > > Hello. > > I hear about new Monitor implementation based on new primitives. > Where to get it?

On Fri, Jan 8, 2016 at 1:20 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

...

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Eliot, please, you told me you had the code and Denis is interested. It uses 3 primitives for performance.

Here are the two business methods: CriticalSection methods for mutual exclusion critical: aBlock "Evaluate aBlock protected by the receiver." ^self primitiveEnterCriticalSection ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]

critical: aBlock ifLocked: lockedBlock "Answer the evaluation of aBlock protected by the receiver. If it is already in a critical section on behalf of some other process answer the evaluation of lockedBlock." ^self primitiveTestAndSetOwnershipOfCriticalSection ifNil: [lockedBlock value] ifNotNil:[:alreadyOwner| alreadyOwner ifTrue: [aBlock value] ifFalse: [aBlock ensure: [self primitiveExitCriticalSection]]]

and the primitives: primitiveEnterCriticalSection primitiveExitCriticalSection primitiveTestAndSetOwnershipOfCriticalSection

Reading this vm code...

primitiveExitCriticalSection | criticalSection owningProcessIndex owningProcess | criticalSection := self stackTop. "rcvr" owningProcessIndex := ExcessSignalsIndex. (self isEmptyList: criticalSection) ifTrue: [objectMemory storePointerUnchecked: owningProcessIndex ofObject: criticalSection withValue: objectMemory nilObject] ifFalse: [owningProcess := self removeFirstLinkOfList: criticalSection. objectMemory storePointerUnchecked: owningProcessIndex ofObject: criticalSection withValue: owningProcess. self resume: owningProcess preemptedYieldingIf: preemptionYields]

I suspect a problem since it does not check it is the owningProcess before setting owningProcess to nil. AFAIK, only the owning process should be able to release the mutex. To demonstrate, evaluating the following...

Transcript clear. cs := CriticalSection new. sync := Semaphore new. b1 := [ Transcript crShow: '1A'. cs primitiveEnterCriticalSection. sync wait. Transcript crShow: '1B'. cs primitiveExitCriticalSection. ]. b2 := [ Transcript crShow: '2A'. cs primitiveEnterCriticalSection. Transcript crShow: '2B'. cs primitiveExitCriticalSection. ]. b3 := [ Transcript crShow: '3A'. cs primitiveExitCriticalSection. cs primitiveEnterCriticalSection. Transcript crShow: '3B'. ]. [ b1 newProcess resume. b2 newProcess resume. 2 second wait. sync signal. ] fork

correctly produces... 1A 2A "pauses here" 1B 2B

but if the last forked block replaces b2 with b3... [ b1 newProcess resume. b3 newProcess resume. 2 second wait. sync signal. ] fork

it produces incorrectly result...

1A 3A 3B "pauses here" 1B

I believe the "cs primitiveExitCriticalSection" in b3 should raise an error. Thus primitiveExitCriticalSection might be...

primitiveExitCriticalSection argumentCount > 0 ifTrue: [ criticalSection := self stackValue: 1. "rcvr" activeProc := self stackTop ] ifFalse: [ criticalSection := self stackTop. "rcvr" activeProc := self activeProcess ]. owningProcessIndex := ExcessSignalsIndex. owningProcess := objectMemory fetchPointer: owningProcessIndex ofObject: criticalSection. owningProcess = activeProc ifFalse: self primitiveFail. "<==!!!" (self isEmptyList: criticalSection) ifTrue: [ objectMemory storePointerUnchecked: owningProcessIndex ofObject: criticalSection withValue: objectMemory nilObject] ifFalse: [ owningProcess := self removeFirstLinkOfList: criticalSection. objectMemory storePointerUnchecked: owningProcessIndex ofObject: criticalSection withValue: owningProcess. self resume: owningProcess preemptedYieldingIf: preemptionYields ]

Now I've inserted the additional check without completely understanding the code around it. I've been contemplating (self isEmptyList: criticalSection) off and on for a couple of days and I'm stumped. I only guess it has something to do with a process being suspended while inside the critical section.

Also I guess the ( argumentCount > 0) is so it can be used from the debugger ??

cheers -ben

Hi Denis,

On Jan 17, 2016, at 9:01 AM, Denis Kudriashov dionisiydk@gmail.com wrote:

Hi.

2016-01-17 17:47 GMT+01:00 Ben Coman btc@openinworld.com:

...

I suspect a problem since it does not check it is the owningProcess before setting owningProcess to nil. AFAIK, only the owning process should be able to release the mutex.

Yes. But it is not mutex. It is more abstract thing which allow implement mutex and other concurrency stuff (like ReadWriteLock). That's why I rename CriticalSection to LockOwnership in my proposals. It only contains primitives and no high level methods like #critical:.

Sounds good. Now would be a good time to submit your preferred versions of the primitives which answer the values that make for more natural variable names. I'm about to release new VMs, including a 64-bit Spur JIT. So I could include the new primitives.

On Mon, Jan 18, 2016 at 1:09 AM, Eliot Miranda eliot.miranda@gmail.com wrote:

Hi Denis,

On Jan 17, 2016, at 9:01 AM, Denis Kudriashov dionisiydk@gmail.com wrote:

Hi.

2016-01-17 17:47 GMT+01:00 Ben Coman btc@openinworld.com:

...

I suspect a problem since it does not check it is the owningProcess before setting owningProcess to nil. AFAIK, only the owning process should be able to release the mutex.

Yes. But it is not mutex. It is more abstract thing which allow implement mutex and other concurrency stuff (like ReadWriteLock). That's why I rename CriticalSection to LockOwnership in my proposals.

I find LockOwnership a bit cumbersome. I guess you don't want just Lock but to include the sense of ownership. Would you consider one of these... * Locker "A person or thing that does an action indicated by the root verb" [1] * Lockee "Less commonly added to verbs to form words meaning a person or thing that is the subject of that verb (ie, who or that does an action), especially where a passive sense of the verb is implied." [2] * OwnLock * OwnedLock

[1] https://en.wiktionary.org/wiki/-er#Suffix [2] https://en.wiktionary.org/wiki/-ee#Suffix

cheers -ben

It only contains primitives and no high level methods like #critical:.

Sounds good. Now would be a good time to submit your preferred versions of the primitives which answer the values that make for more natural variable names. I'm about to release new VMs, including a 64-bit Spur JIT. So I could include the new primitives.

On Mon, 18 Jan 2016 11:22:15 +0100 Denis Kudriashov dionisiydk@gmail.com wrote:

To choose better class name we should take into account how we will use it. Could you suggest names for #acquire and #release in context of your class name? ("locker acquire" is not good)

If people think that simple Lock is good for this purpose we can use it.

Perhaps better to think of an "access permission" than a "lock"

uniqueAccess acquire

accessPermission acquire

...? -KenD

On Tue, Jan 19, 2016 at 12:06 AM, KenD Ken.Dickey@whidbey.com wrote:

On Mon, 18 Jan 2016 11:22:15 +0100 Denis Kudriashov dionisiydk@gmail.com wrote:

...

To choose better class name we should take into account how we will use it. Could you suggest names for #acquire and #release in context of your class name? ("locker acquire" is not good)

If people think that simple Lock is good for this purpose we can use it.

Perhaps better to think of an "access permission" than a "lock"

uniqueAccess acquire

Maybe. Except when I think of uniqueXXX what comes to mind is the Singleton pattern.

accessPermission acquire

I think this is a stretch, and invokes thoughts of security and file access.

cheers -ben

On Mon, Jan 18, 2016 at 6:22 PM, Denis Kudriashov dionisiydk@gmail.com wrote:

2016-01-17 19:10 GMT+01:00 Ben Coman btc@openinworld.com:

...

I find LockOwnership a bit cumbersome. I guess you don't want just Lock but to include the sense of ownership. Would you consider one of these...

• Locker "A person or thing that does an action indicated by the

root verb" [1]

• Lockee "Less commonly added to verbs to form words meaning a

person or thing that is the subject of that verb (ie, who or that does an action), especially where a passive sense of the verb is implied." [2]

• OwnLock
• OwnedLock

To choose better class name we should take into account how we will use it. Could you suggest names for #acquire and #release in context of your class name? ("locker acquire" is not good)

You're right. I didn't think it through. I don't have any good alternative message names.

If people think that simple Lock is good for this purpose we can use it.

I think Lock is probably okay but survey a few more opinions. However a generic lock as introduced in most CS lessons that turned up in searches don't have an owner, so maybe my last suggestion OwnedLock is also. For example... lock := OwnedLock new. lock aquire

cheers -ben

2016-01-08 13:06 GMT+01:00 stepharo stepharo@free.fr:

I have a (stupid) question. Is the code running without the primitives? Are the code below the primitives correct? I asked that because we can have 100 eyes and brains on the smalltalk level and far less on the VM primitive level.

Eliot code is used VM primitives for critical sections.

On 7 January 2016 at 17:12, Eliot Miranda eliot.miranda@gmail.com wrote:

Hi Denis, Hi Clément, Hi Frank,

On Thu, Jan 7, 2016 at 5:34 AM, Clément Bera bera.clement@gmail.com wrote:

...

Hello,

Eliot, please, you told me you had the code and Denis is interested.

It uses 3 primitives for performance.

Forgive the delay. I thought it proper to ask permission since the code was written while I was at Qwaq. I'm attaching the code in a fairly raw state, see the attached. The code is MIT, but copyright 3DICC.

It is a plugin replacement for Squeak's Mutex, and with a little ingenuity could be a replacement for Squeak's Monitor. It is quicker because it uses three new primitives to manage entering a critical section and setting the owner, exiting the critical section and releasing the owner, and testing if a critical section, entering if the section is unowned. The use of the primitives means fewer block activations and ensure: blocks in entering and exiting the critical section, and that's the actual cause of the speed-up.

You can benchmark the code as is. Here are some results on 32-bit Spur, on my 2.2GHz Core i7

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n

• 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1].

cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

{Mutex new. Monitor new. CriticalSection new} collect: [:cs| | n | n := 0. cs class name, ' -> ', [cs critical: [n := n + 1]. cs critical: [n := n + 1]. cs critical: [n := n

• 1]. cs critical: [n := n + 1]. cs critical: [n := n + 1].

cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. cs critical: [n := n - 1]. n ] bench]

#( 'Mutex -> 440,000 per second. 2.27 microseconds per run.' 'Monitor -> 688,000 per second. 1.45 microseconds per run.' 'CriticalSection -> 1,110,000 per second. 900 nanoseconds per run.')

Replacement is probably trivial; rename Mutex to OldMutex, rename CriticalSection to Mutex, recompile. But there are lots of mutexes in the system and these are potentially owned. Transforming unowned ones is trivial, but transforming owned ones is, I think, impossible. But at least in my system there are no owned mutexes or monitors.

Frank (or anyone else), would you be interested in creating a replacement for Squeak's Monitor based on CriticalSection?

It sounds like an interesting problem. I watched the thread unfold and I'm still not massively clear on what is required though? (Apologies for the delay in responding: my cup overfloweth at the moment, but should resume normal levels in a month or so.)

frank