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Re: [Qemu-devel] [PATCH for-2.8?] rules.mak: speedup save-vars load-vars

From: Fam Zheng
Subject: Re: [Qemu-devel] [PATCH for-2.8?] rules.mak: speedup save-vars load-vars
Date: Thu, 3 Nov 2016 14:16:19 +0800
User-agent: Mutt/1.7.1 (2016-10-04)

On Wed, 11/02 17:24, Paolo Bonzini wrote:
> Unnesting variables spends a lot of time parsing and executing foreach
> and if functions.  Because actually very few variables have to be
> saved and restored, a good strategy is to remember what has to be done
> in load-vars, and only iterate the right variables in load-vars.
> For save-vars, unroll the foreach loop to provide another small
> improvement.
> This speeds up a "noop" build from around 15.5 seconds on my laptop
> to 11.7 (25% roughly).
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>       I'm wondering if this would be acceptable for 2.8.

I think that's fine if you don't want to bear the slowness in 2.8. But TBH I
haven't really noticed this as an issue myself. Anyway,

Reviewed-by: Fam Zheng <address@hidden>

>       I also have sent patches to GNU make that save another
>       20%, down to 9.8 seconds.

Wow, is there a link to the patch?


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