-------- Original Message -------- Subject: Re: [squeak-dev] How weak finalization affects the performance Date: Tue, 26 Oct 2010 03:30:13 -0400 From: Andres Valloud <avalloud@smalltalk.comcastbiz.net> Reply-To: andres.valloud@gmail.com <andres.valloud@gmail.com>, The general-purpose Squeak developers list <squeak-dev@lists.squeakfoundation.org> To: The general-purpose Squeak developers list <squeak-dev@lists.squeakfoundation.org> Why does finalization do any work when running a block which I think just creates garbage? Is finalization on a per class basis (i.e.: the VM notifies the image that some objects might be notified, and the image just enumerates through them), or on a per object basis (i.e.: the VM maintains a finalization queue as in VisualWorks)? On 10/26/10 0:25 , Igor Stasenko wrote:

Here the idea, which came to Chris, put a delay into #finalizationProcess loop:

finalizationProcess [true] whileTrue: [ WeakFinalizationList initTestPair. FinalizationSemaphore wait. FinalizationLock critical: [ WeakFinalizationList checkTestPair. FinalizationDependents do: [:weakDependent | weakDependent ifNotNil: [weakDependent finalizeValues]]] ifError: [:msg :rcvr | rcvr error: msg]. 5 seconds asDelay wait. ].

And here a simple benchmark, which triggers GC often:

[ Array new: 100 ] bench

without delay:

'2,450,000 per second.' '2,490,000 per second.' '2,490,000 per second.' '2,480,000 per second.' '2,530,000 per second.'

with delay:

'2,670,000 per second.' '2,680,000 per second.' '2,690,000 per second.' '2,730,000 per second.'

roughly about ~8% faster :)

But now lets put something big into weak array:

| dict b | dict := WeakKeyDictionary new addAll: (( 1 to: 1000 ) collect: [:i | i->i] ); yourself. WeakArray addWeakDependent: dict. b := [ Array new: 100 ] bench. WeakArray removeWeakDependent: dict. b

without delay:

'1,840,000 per second.' '2,060,000 per second.' '2,130,000 per second.'

with delay:

'3,030,000 per second.' '2,880,000 per second.' '2,890,000 per second.'

Do not forget to do: WeakArray restartFinalizationProcess

when you changing the #finalizationProcess method, otherwise you won't see real numbers.

So, i like the idea of putting delay there. Finalization is eventual, and there is no hard guarantees that it will happen in micro-second just after some object become garbage. So, be it 5 seconds or 1000 seconds not really matters. What is matters that with delay we win much more, by avoiding wasting time in finalization process too often.