[Vm-dev] OS X Mavericks & cog tickers

[Igor Stasenko]

On 25 October 2013 01:18, John McIntosh <johnmci at smalltalkconsulting.com>wrote:

>
> Well let me reflect.
> Nothing has changed, the VM energy sapping field is the same as
>  yesterday, just more evident.
>
>  I wasn't able to determine what code base is used, but if I go back 5 or
> 10 years.
>
> (a) The morphic event polling cycle runs 50 times a second. One could
> write some timer consolidation code there to consider when do I have to
> wake up and paint all those morphs? No C/Objective-C/assembler/fortran
> required...
>
> (b) Maybe the VMs are event driven now and Morphic does not need to poll
> 50 times a second?
>
> (c) The BSD Unix socket system requires polling of some form.  But see
> work by Craig 10-15 back on "Flow"
>
> (d) When all the Smalltalk Processes settle, the dispatcher runs the
> lowest priority task which calls relinquishProcessorForMicroseconds with
> a bogus value.
>
>
(e) Cog uses heartbeat timer to interrupt interpreter at regular time
periods
what can be done, i think it to suppress heartbeat, during
relinquishProcessorForMicroseconds execution.
but that won't buy much, unless we increase the time period to sleep to be
times larger than heartbeat cycle (both are 1ms).

sqMacV2Time.c:

sqInt ioRelinquishProcessorForMicroseconds(sqInt microSeconds) {
    //API Documented
    /* This operation is platform dependent.      */
    #pragma unused(microSeconds)

    sqInt       realTimeToWait,now,next;
    extern sqInt getNextWakeupTick(void);                //This is a VM
Callback
    extern sqInt setInterruptCheckCounter(sqInt value);  //This is a VM
Callback

    setInterruptCheckCounter(0);
    now = ioMSecs();
    next = getNextWakeupTick();

    /*BUG??? what if clock wraps? */

    if (next <= now)
        if (next == 0)
                realTimeToWait = 16;
            else {
                return 0;
            }
        else
            realTimeToWait = next - now;

    aioSleep((int) realTimeToWait*1000);
    return 0;
}


The real solution would be to not fall asleep,
but just put process into waitable state on 'wake up semaphore'
which then signaled if there's some i/o or timeout.


>
>
> On Thu, Oct 24, 2013 at 6:21 PM, tim Rowledge <tim at rowledge.org> wrote:
>
>>
>> Looking through some of the low-level changes in Mavericks I noticed
>> stuff about timer consolidation. I *think* that it is something that you
>> can offer to allow, rather than something done unto you code, but almost
>> certainly it will have some sort of impact on the heartbeat ticker type of
>> code used in stackvm/cog. Where is a skilled Mac vm maintainer when you
>> need one?
>>
>> tim
>> --
>> tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
>> "bOtHeR" said Pooh, mistaking the LSD tablet for aspirin
>>
>>
>>
>
>
> --
> ===========================================================================
> John M. McIntosh <johnmci at smalltalkconsulting.com>
> Corporate Smalltalk Consulting Ltd. Twitter: squeaker68882
> ===========================================================================
>
>
>


-- 
Best regards,
Igor Stasenko.
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