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Message-ID: <c30d70960810222354i11820b4bv92263fde983d99b9@mail.gmail.com>
Date: Thu, 23 Oct 2008 10:54:54 +0400
From: "Alexei Fedotov" <alexei.fedotov@gmail.com>
To: dev@harmony.apache.org
Subject: Re: [performance] Startup cost is high for Harmony (HARMONY-6002)
In-Reply-To: <9623c9a50810222321s5ea62c36iad36c3e1c0ff8ef8@mail.gmail.com>
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References: <1001978583.1224684584498.JavaMail.jira@brutus>
	 <48FF8D0F.7010206@gmail.com>
	 <c30d70960810222244s68a3ef3ax30759ac07ad305ef@mail.gmail.com>
	 <9623c9a50810222321s5ea62c36iad36c3e1c0ff8ef8@mail.gmail.com>

Xiao Feng,
Thanks for a good question.

The optimization improves so-called "peak score" which is calculated
from several subsequent executions. If you cache VM state in different
files for different command lines, you may even cache pre-compiled
class files for a particular benchmark. As I've got from a fellow SPEC
committee member this optimization is allowed unless the released VM
is specifically tuned to pass the spec.

Sorry about the third bullet. Well, I thought if I should mention
pre-compiled classes there. I hesitate because I don't know any
trusted research which shows that loading pre-compiled classes from
disk is quicker than dynamic re-compilation.

Thanks!

On Thu, Oct 23, 2008 at 10:21 AM, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> On Thu, Oct 23, 2008 at 1:44 PM, Alexei Fedotov
> <alexei.fedotov@gmail.com> wrote:
>> Hello Wenlong,
>> You have addressed a very interesting topic. Let me share few ideas
>> how to approach it:
>>
>> 1. The first thing I would expect to understand here is why we should
>> care about "Hello, World" startup. SPEC jvm [0] startup scores are
>> much more tempting to approach. Then one should compare the score with
>> one of our competitors. Taking into account that 300 ms = 300 context
>> switches I would not say that the number itself makes me unhappy about
>> Harmony speed.
>>
>> 2. Due to some bureaucracy the following tempting [1] idea is still
>> waiting for an experienced and accurate C coder to complete:
>>  * load classes into bootstrap class loader once
>>  * store the internal representation of classes as a memory mapped file;
>>  * next time, load the file if it exists.
>
> Fedotov, thanks. I guess this idea can only improve the second-time
> startup time? Is this be useful for SPECJVM startup score? Thanks.
>
> Btw, your email lost bullet 3. :)
>
> Thanks,
> xiaofeng
>
>> 4. If you don't like C, there are tunable things in a class library
>> you may find using Gregory's JVMTI profiler [2].
>>
>> [0] http://www.spec.org/jvm2008/
>> [1] a research shows +10% on "Hello, World"
>> [2] two first attachments at https://issues.apache.org/jira/browse/HARMONY-4569
>>
>> On Thu, Oct 23, 2008 at 12:29 AM, Tim Ellison <t.p.ellison@gmail.com> wrote:
>>>
>>> Wenlong Li (JIRA) wrote:
>>> > The startup time is long for the simple helloworld program. On a Core
>>> > 2 Quad-core processor, running the simple helloworld program will take
>>> > more than 300 ms.
>>> > Can we reduce the startup cost?
>>>
>>> Yes, I hope so ... concrete suggestions or analysis of startup costs are
>>> welcome.
>>>
>>> Regards,
>>> Tim
>>
>>
>>
>> --
>> With best regards,
>> Alexei
>>
>
>
>
> --
> http://xiao-feng.blogspot.com
>


-- 
With best regards,
Alexei