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Re: [PATCH 0/5] tcg: Dynamically allocate temporaries

From: Richard Henderson
Subject: Re: [PATCH 0/5] tcg: Dynamically allocate temporaries
Date: Thu, 21 Jan 2021 10:17:08 -1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

On 1/21/21 10:09 AM, BALATON Zoltan wrote:
> On Wed, 20 Jan 2021, BALATON Zoltan wrote:
>> On Tue, 19 Jan 2021, Richard Henderson wrote:
>>> My recent change for caching tcg constants has, in a number of cases,
>>> overflowed the statically allocated array of temporaries.  Change to
>>> dynamic allocation.
>> This seems to work for me so
>> Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
>> but have you done any performance tests to check that this actually improves
>> emulation speed? To mee it seems slower. Booting AmigaOS on sam460ex with
>> c0dd6654f207 (just before your TCG series) takes:
>> real    0m33.829s
>> user    0m34.432s
>> sys    0m0.296s
>> but on HEAD with this series:
>> real    0m44.381s
>> user    0m46.058s
>> sys    0m0.532s
>> This is noticable decrease in speed also without measuring it. With just
>> increasing the TCG_MAX_TEMPS to 2048 on 7c79721606be without this series I 
>> get:
>> real    0m42.681s
>> user    0m44.208s
>> sys    0m0.435s
>> So the performance regression is somewhere in the original series not in this
>> fix up series.
> I've tried to do more measurements to identify where it got slower but I could
> not reproduce it today. I'm now getting around 42 seconds both before and 
> after
> the series so not sure what made it faster before but it's probably not 
> because
> of a code change then.

That's reassuring.  I hadn't been able to measure a performance regression 

(The kind of TB that caused this SEGV thread and creates oodles of temps seems
to be an outlier.  Otherwise there should be very little change to non-vector


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