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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: [general][performance] Stefan Krause's Harmony performance evaluation
Date Fri, 04 Jul 2008 08:56:19 GMT
Good findings!! Thanks. -xiaofeng

2008/7/4 Aleksey Shipilev <aleksey.shipilev@gmail.com>:
> Hi Gregory, all,
>
> The performance is important for JRE too.
>
> BTW, I had profiled spectralnorm benchmark and see following problems:
>
> 1. Bad instruction selection for integer divide:
>
> int a;
> int b = a / 2;
>
> generates into:
>
> mov eax, a
> mov ebx, 2
> idiv eax, ebx
>
> but it's better to
>
> mov eax, a
> shl eax, 1
>
> Manual change in Java code brings +60% to spectralnorm performance
> (execution time downs from 10secs to 6secs). There should be better
> instruction selection for divide operation. Would someone take it? If
> not, I would try to produce the patch for Jitrino this weekend.
>
>
> 2. Recompilation events propagation
>
> Consider the following call chain:
> main() --[n times]--> A() --[m times]--> B()
>
> Now consider, m >> n, then B() should be inlined. But such the
> inlining will be done during the recompilation of method A(), which
> waits for n to rise up (that's true for current server.emconf with
> edge profiler enabled). On first glance, one of the solutions will be
> propagation of such recompilation requests up the call chain. Any
> ideas here are welcome.
>
> Thanks,
> Aleksey.
>
> On Fri, Jul 4, 2008 at 1:04 AM, Gregory Shimansky <gshimansky@apache.org> wrote:
>> On 4 июля 2008 Aleksey Shipilev wrote:
>>> TWIMC,
>>>
>>> Stefan Krause publishes another review on Java vs. C performance here:
>>> http://www.stefankrause.net/wp/?p=9#comments
>>>
>>> It seems like Harmony has "a long way to go" in performance :)
>>> I'm gonna look on some of these tests in near term.
>>
>> It is interesting to see that IBM is often quite close to Harmony in
>> performance. In fact Harmony acts quite well in its current state. I think
>> though that performance for Java is always a 2nd priority after stability.
>> Look at IBM, its Java is targeted at servers where stability is what is
>> important.
>>
>> Looking at the occasional test failures on the alerts mail list it seems like
>> stability is the number one focus for improvement and it is a by far harder
>> to move in that direction.
>>
>> --
>> Gregory
>>
>



-- 
http://xiao-feng.blogspot.com
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