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Re: [Qemu-devel] [PATCH 2/3] Get rid of temporary variable cache.
From: |
Filip Navara |
Subject: |
Re: [Qemu-devel] [PATCH 2/3] Get rid of temporary variable cache. |
Date: |
Mon, 29 Jun 2009 20:57:17 +0200 |
On Mon, Jun 29, 2009 at 8:34 PM, Paul Brook<address@hidden> wrote:
> On Monday 29 June 2009, Filip Navara wrote:
>> The temporary variable cache actually hurts TCG more than it helps.
>> Empirical results show that when running the Dhrystone benchmark with this
>> patch improves the speed by about 2%.
>
> I find it hard to believe this patch has any significant effect on runtime,
> other than random variation. My guess is it spends almost all of its time in a
> few guest loops, and no time doing translation. I'd expect the generated code
> should be the same before and after.
You are right. That will teach me not to trust benchmarks and validate
the results by other means also.
> I'm not saying this patch is a bad idea (new_tmp/dead_tmp predate
> tcg_temp_free and are now redundant), just that I don't believe your benchmark
> results.
And you were right not to believe them. Thanks for looking at the patch.
Best regards,
Filip Navara