[Vm-dev] CogVM performance

[Eliot Miranda]

Hi Levente,

On Sat, May 16, 2015 at 8:59 AM, Levente Uzonyi <leves at elte.hu> wrote:

>
> On Sat, 16 May 2015, Esteban Lorenzano wrote:
>
>
>>
>>  On 16 May 2015, at 17:08, Levente Uzonyi <leves at elte.hu> wrote:
>>>
>>> Hi All,
>>>
>>> I saw that some of my benchmarks produce different results when running
>>> on PharoVM instead of CogVM, and I was wondering why. I ran #tinyBenchmarks
>>> from the same image on both VMs and the results were surprising:
>>>
>>> "CogVM 3343" '904593639 bytecodes/sec; 46368169 sends/sec'
>>> "Pharo vm50" '941176470 bytecodes/sec; 120698445 sends/sec'
>>>
>>> Slightly more bytecodes, and a lot more sends. I tried playing with
>>> compiler flags, but with no luck, so I came to the conclusion that the
>>> difference comes from somewhere else. I checked where the PharoVM was
>>> forked from CogVM (somewhere around 2014-06-10), so I downloaded a version
>>> of CogVM from around that time: CogVM 3048.
>>>
>>> And the results are '932604735 bytecodes/sec; 118660385 sends/sec'.
>>>
>>> Somewhere between 3048 and 3343 the performance has dropped
>>> significantly (sends/sec). Note that this is not something that's only
>>> visible in micro benchmarks.
>>>
>>> Does anyone know why?
>>>
>>
>> It has to be a flags issue.
>>
>
> I don't think so, because flags don't have much effect on jitted code. I
> can squeeze out a few percents with -O3 -fomit-frame-pointer -march=native,
> but what that really affects are the primitives.
>
> I narrowed it down, it happened between 3306 and 3308:
>
> 3048 '932604735 bytecodes/sec; 118660385 sends/sec'
> 3163 '885813148 bytecodes/sec; 118216795 sends/sec'
> 3164 '856187290 bytecodes/sec; 109993018 sends/sec'
> 3254 '932604735 bytecodes/sec; 119670738 sends/sec'
> 3306 '943778801 bytecodes/sec; 125949728 sends/sec'
> 3308 '924187725 bytecodes/sec; 44489533 sends/sec'
> 3311 '937728937 bytecodes/sec; 46190853 sends/sec'
> 3312 '894323144 bytecodes/sec; 45239356 sends/sec'
> 3343 '904593639 bytecodes/sec; 46368169 sends/sec'
>


I'll take a look soon.  Could you tell me what platform you're on?

[snip]
-- 
best,
Eliot
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