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Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by de
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default |
Date: |
Mon, 7 Feb 2011 14:03:50 -0200 |
User-agent: |
Mutt/1.5.20 (2009-08-17) |
On Mon, Feb 07, 2011 at 08:12:55AM -0200, Marcelo Tosatti wrote:
> > > One more thing I didn't mention on the email-thread or on IRC is
> > > that last time I checked, qemu with io-thread was performing
> > > significantly slower than non io-thread builds. That was with
> > > TCG emulation (not kvm). Somewhere between 5 - 10% slower, IIRC.
>
> Can you recall what was the test ?
>
> > > Also, although -icount & iothread no longer deadlocks, icount
> > > still sometimes performs incredibly slow with the io-thread (compared
> > > to non-io-thread qemu). In particular when not using -icount auto but
> > > a fixed ticks per insn values. Sometimes it's so slow I thought it
> > > actually deadlocked, but no it was crawling :) I haven't had time
> > > to look at it any closer but I hope to do soon.
Edgar, please give the attached patch a try with fixed icount value. The
calculation for next event makes no sense for iothread timeout, only for
vcpu context.
> > >
> > > These issues should be fixable though, so I'm not arguing against
> > > enabling it per default. Just mentioning what I've seen FYI..
> >
> > Right, remember seeing 20% added overhead for network copy with TCG on
> > the initial iothread merge.
>
> This is not the case anymore, network transfer speed is comparable.
> Probably due to SIG_IPI delivery being reliable, which was fixed later.
Is there any other issue that prevents turning CONFIG_IOTHREAD on by
default?
qemu-fix-icount-timeout-iothread.patch
Description: Text document
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Marcelo Tosatti, 2011/02/07
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default,
Marcelo Tosatti <=
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Paolo Bonzini, 2011/02/07
- [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Jan Kiszka, 2011/02/07
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Aurelien Jarno, 2011/02/07
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Aurelien Jarno, 2011/02/08
- [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Paolo Bonzini, 2011/02/08
- [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Jan Kiszka, 2011/02/08
- [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Aurelien Jarno, 2011/02/08
- Re: [Qemu-devel] Re: [PATCH 2/7] Enable I/O thread and VNC threads by default, Anthony Liguori, 2011/02/08