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From Tim Ellison <t.p.elli...@gmail.com>
Subject Re: [classlib] HashMap optimization (again)
Date Thu, 10 Jan 2008 20:53:32 GMT
Aleksey Shipilev wrote:
> a little update here. I have managed to split problematic method into
> two chunks, I will attach new patch to JIRA in few minutes. So far the
> picture is following:

So this is an attempt to make the method small enough (measured in 
what?) to be inlined by the JIT, right?  Is there a way to annotate the 
JIT to always in-line it, say by name, rather than juggling the size?

> Windows x86_64:
>  100% Harmony-clean
>  97.7% Harmony-clean + H5374 (old)
>  99.6% Harmony-clean + H5374 (new)
> Windows x86:
>  100% Harmony-clean
>  97.9% Harmony-clean + H5374 (old)
>  99.6% Harmony-clean + H5374 (new)

What benchmark are you using?  I saw this specialization technique give 
a reasonable boost on SPECjbb2005, with IBM VME not DRLVM, and was 
hoping it would be applicable here too.  Avoiding the value dereference 
enhances data locality and thereby fewer CPU cache misses.

> I will spend more time considering what can be done to beat current
> implementation, gathering new profile and making accurate
> measurements. But since there is a little degradation remain, I would
> propose to wait some more time for clearer picture. What do you think?

I think we should only apply the patch if it produces a benefit to Harmony.


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