From: Anthony Liguori <anthony@codemonkey.ws>
To: Anders <mail@flac.kalibalik.dk>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [4341] qemu: generate signals on tap I/O
Date: Mon, 05 May 2008 21:48:31 -0500 [thread overview]
Message-ID: <481FC6FF.3060802@codemonkey.ws> (raw)
In-Reply-To: <481F9449.6040602@flac.kalibalik.dk>
Anders wrote:
> Anthony Liguori wrote:
>> You're seeing improvement with normal QEMU? Can you please post a
>> description of what you're seeing improve with SIGIO. SIGIO should
>> really only slow things down.
>>
>
> I found this issue in KVM. I have not timed in QEMU, but the issue
> seemed generic, so I posted it upstream.
Right, this was an artifact of how KVM handled select. It's not generic
at all.
> My usecase was a new VNC connection delaying until the next timer tick
> (which is a really long time in some KVM configurations).
>
> The improvement is from running the select() immediately, rather than
> waiting around for a timer to expire.
In KVM today, select() is in it's own thread so it will service IO
immediately. This makes SIGIO unnecessary (not quite correct yet but
will be very soon).
Regards,
Anthony Liguori
> Thanks,
> Anders.
>
next prev parent reply other threads:[~2008-05-06 2:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-05 21:26 [Qemu-devel] [4341] qemu: generate signals on tap I/O Aurelien Jarno
2008-05-05 22:06 ` Anders
2008-05-05 22:15 ` Aurelien Jarno
2008-05-05 22:42 ` Anders
2008-05-05 22:44 ` Anthony Liguori
2008-05-05 22:49 ` Aurelien Jarno
2008-05-05 22:51 ` Aurelien Jarno
2008-05-05 22:57 ` Anthony Liguori
2008-05-05 23:00 ` Anthony Liguori
2008-05-05 23:12 ` Anders
2008-05-06 2:48 ` Anthony Liguori [this message]
2008-05-06 8:35 ` Anders
2008-05-05 22:50 ` Anthony Liguori
2008-05-05 22:43 ` Anthony Liguori
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