[ANN] Magma 1.0r40

[Chris Muller]

> I'm placed a line in removeGarbageCollectedObjectEntries
> Transcript show: 'Oids count: ' , self oidCount asString; cr.
> And during running Florian's update it shows (between other lines):
> Oids count: 29923
> Oids count: 45449
> Oids count: 49919
> Oids count: 66399
> Oids count: 76492
> So its growing and growing..
> And only way to get rid of dead keys, is to call MaOidManager>>finalizeOids.
> But i can't find any places, leading to call of this method. Is this
> designed to be managed by user directly, using
> MagmaSession>>finalizeOids ?

Yes, as documented in the performance tuning page

    http://wiki.squeak.org/squeak/2985

at this time finalizeOids is intended to be called by the user,

> I think it should call finalizeValues to dicts in
> removeGarbageCollectedObjectEntries, so both dicts with object>id and
> id>object associations will be cleaned and rehashed.

but that sounds like a good idea.  I know these two cleaning
mechanisms were tacked on years apart from each other, so maybe that's
why they ended up separate mechanisms.

Of course, all this is just to accomodate less than ideal Weak
Dictionary's included with Squeak.
I'd much rather fix or replace the Dictionary's.  Florian, have you
tried any alternative Weak Dictionary's available?  Be sure to check
out Martin Loewis' and Sig's.  (I've posted the link to Martin's
several times in the last months, it's on Mantis).

> Or, maybe, since magma uses own version(s) of weakIdentityKey dicts,
> implementation of #at:put: in weakIdentityKey dict can be changed to
> silently reuse entries with key=nil. So there will be much less need
> for rehashing.

MaDictionary is a dead-simple hack around the 12-bit identity hash
limitation.  Whenever standard WeakIdentityDictionary's get over 4K
elements their performance suffers tremendously, so MaDictionary makes
the degradation more linear by managing a collection of <4K sized
Dictionary's.

I really don't want to make the Ma Dictionary's more complicated.  I
really would just like to replace them with something built from the
ground up to scale to more than 4K elements.

> it. But then i wonder, why with big pauses putted in #reject: (or not
> using #reject: , as in new case) helped to avoid errors?

I have never seen the errors myself.  Do they happen with the stock
Magma MaDictionary's?  If so, how can I reproduce it?

> Interesting, how well magma handles following code:
> session commit: [
>   [ big long huge loop ] fork.
>   [ big long huge loop 2 ] fork.

Do NOT do that.  However, you should be able to do this:

[ big long huge loop with multiple commits ] fork.
[ big long huge loop 2 with multiple commits ] fork.

> Is it allows to spawn different processes in commit?

No.

> I now trying to run update with all methods in MagmaOidManager
> enclosed by mutex.

Thanks Sig, I hope we can find a lean, mean, fast Dictionary machine
for the next Magma.

 - Chris