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Re: [Qemu-devel] Significant performance regression in qemu-system-mips.
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] Significant performance regression in qemu-system-mips. |
Date: |
Thu, 1 Apr 2010 23:33:09 +0200 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
On Wed, Mar 24, 2010 at 03:34:00PM -0500, Rob Landley wrote:
> I have a native build under qemu that gets killed if it doesn't produce a
> line
> of output for 60 seconds (hang detection enforced by the host monitoring
> qemu's stdout with --nographic, not from within qemu).
>
> In the most recent release version, it never came close to triggering on mips
> with a 30 second timeout. In the current -git version (well, as of Thursday
> anyway), it triggers frequently (about 90% of the time) even with a 60 second
> timeout.
>
> I bisected it to this:
>
> commit 1828be316f6637d43dd4c4f5f32925b17fb8107f
> Author: Paolo Bonzini <address@hidden>
> Date: Wed Mar 10 11:38:41 2010 +0100
>
> more alarm timer cleanup
>
> The timer_alarm_pending variable is related to the alarm timer but not
> placed in the struct. Also, in qemu_mod_timer the wrong flag was being
> tested: the timer is rearmed in the alarm timer "bottom half", so the
> right flag to test there is the "pending" flag.
>
> Finally, I hoisted the NULL checks from alarm_has_dynticks to
> host_alarm_handler.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Anthony Liguori <address@hidden>
>
> Reverting that patch fixed it (git show HEAD | patch -R -p1), by which I mean
> three consecutive runs with 30 second timeout didn't trigger the hang
> detection.
>
I have tried to reproduce the issue by measuring the boot time of a mips
system, but it stay unchanged between before and after the patch. Do you
have some more details about how to reproduce the issue ? Have you tried
to pay with the -clock option?
--
Aurelien Jarno GPG: 1024D/F1BCDB73
address@hidden http://www.aurel32.net