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Re: [Qemu-devel] [RESEND][PATCH 0/3] Fix guest time drift under heavy lo


From: Anthony Liguori
Subject: Re: [Qemu-devel] [RESEND][PATCH 0/3] Fix guest time drift under heavy load.
Date: Tue, 11 Nov 2008 11:26:40 -0600
User-agent: Thunderbird 2.0.0.17 (X11/20080925)

Gleb Natapov wrote:
On Mon, Nov 10, 2008 at 09:46:12AM -0600, Anthony Liguori wrote:
Gleb Natapov wrote:
On Mon, Nov 10, 2008 at 09:24:55AM -0600, Anthony Liguori wrote:
Gleb Natapov wrote:
On Sun, Nov 09, 2008 at 10:36:59AM -0600, Anthony Liguori wrote:
Otherwise, I'm curious if you have any insight into where we're pausing for 10ms that's causing the missed interrupt?

Don't know yet.
What's your full command line?

/home/gleb/install/qemu/org/bin/qemu-system-x86_64 -hda Windows2003.raw -m 1024 
-net
nic,model=rtl8139 -net user -vnc 172.17.10.111:1 -usbdevice tablet
-usbdevice tablet may be the culprit.  Is the guest doing an significant IO?

-usbdevice tablet has nothing to do with it. Qemu misses interrupt even
without this option and with SDL screen it misses them in bunches when
SDL redraws a screen. In case of vnc qemu misses interrupt because of
fsync() call in raw_flush(), or so my instrumentation shows.

eek, fsync is actually wrong here because there may be pending requests in flight that fsync won't take into account. We should be doing an aio_fsync(). You're using IDE right?

Regards,

Anthony Liguori

--
                        Gleb.





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