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Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debuggin
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases |
Date: |
Sat, 11 May 2013 09:23:32 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, May 10, 2013 at 10:59:22PM +0200, Paolo Bonzini wrote:
> Il 10/05/2013 19:41, Anthony Liguori ha scritto:
> > Paolo Bonzini <address@hidden> writes:
> >
> >> Il 10/05/2013 16:39, Anthony Liguori ha scritto:
> >>> I just oppose the notion of disabling casts and *especially* only
> >>> disabling casts for official builds.
> >>
> >> This actually happens all the time. Exactly this kind of type-safe cast
> >> is disabled in releases of GCC, but enabled when building from svn trunk.
> >
> > Let's assume for a moment that you are right and this behavior is what
> > we should have. Let's also assume there is a real regression here
> > which has yet to have been established.
>
> Aurelien timed the effect of my patch two hours before you sent this
> message. If it's not a regression in 1.5 (which is quite obvious from
> the profile), it is a regression from the introduction of CPU classes
> (1.3 or 1.4), when this code didn't exist at all.
>
> And in 1.5 we introduced virtio-net casts as well (or did mst sneak in
> his change anyway? ;)). If 10% is the effect of a few hundred
> interrupts/sec, perhaps the same effect is visible on a few thousand
> packets/sec. I wouldn't bet against that one week from release.
I have run perf top on a KVM x86-64 instance running iperf. I measured
around 3% of the CPU taken by g_hash_table_lookup + g_str_hash +
__strcmp_sse42. I don't know how it was before though.
--
Aurelien Jarno GPG: 1024D/F1BCDB73
address@hidden http://www.aurel32.net
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, (continued)
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Paolo Bonzini, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Aurelien Jarno, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Paolo Bonzini, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Aurelien Jarno, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Paolo Bonzini, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Paolo Bonzini, 2013/05/11
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases,
Aurelien Jarno <=
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Aurelien Jarno, 2013/05/10
- Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Andreas Färber, 2013/05/10
Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Aurelien Jarno, 2013/05/10
Re: [Qemu-devel] [PATCH for-1.5 0/9] Disable expensive QOM cast debugging for official releases, Anthony Liguori, 2013/05/13