Re: [Qemu-devel] [PATCH 5/7] tcg-i386: Implement deposit operation.

[Aurelien Jarno <aurelien@aurel32.net>]

Hi,

On Tue, Jan 25, 2011 at 01:27:49PM +0100, Edgar E. Iglesias wrote:
> On Mon, Jan 10, 2011 at 07:23:46PM -0800, Richard Henderson wrote:
> > Special case deposits that are implementable with byte and word stores.
> > Otherwise implement with double-word shift plus rotates.
> > 
> > Expose tcg_scratch_alloc to the backend for allocation of scratch registers.
> > 
> > Signed-off-by: Richard Henderson <rth@twiddle.net>
> 
> Hi,
> 
> I've tested this patch a bit and got mixed results. I tested with patched
> CRIS and MicroBlaze translators. The patch works OK (it doesn't break
> anything) for the usecases I had but I saw a bit of a slowdown with
> MicroBlaze (compare to not using deposit at all).
> 

This week-end I have tested it emulating an x86-64 machine on x86-64,
with all the patch series applied. I have measured the boot time from
the bootloader up to the graphical environment of a Debian installation
I used -snapshot to make sure the host hard-drive is not introducing any
noise in the measurement (so that the whole image is in the host cache),
and did the measurement 10 times. The machine is a Core 2 Q9650, nothing
else was running on the machine except the few standard daemons.

I have found that the boot time is roughly 1.8% faster with the patch
series applied. It's undoubtedly an improvement, but still close to the
measurement noise. This is a bit disappointing...

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net