From: Stefan Hajnoczi <stefanha@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Pekka Enberg <penberg@kernel.org>, Alexander Graf <agraf@suse.de>,
Anthony Liguori <anthony@codemonkey.ws>,
Prasad Joshi <prasadjoshi124@gmail.com>,
Avi Kivity <avi@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sasha Levin <levinsasha928@gmail.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Asias He <asias.hejun@gmail.com>,
Jens Axboe <jaxboe@fusionio.com>
Subject: Re: [ANNOUNCE] Native Linux KVM tool v2
Date: Thu, 16 Jun 2011 10:09:01 +0100 [thread overview]
Message-ID: <BANLkTi=j1EqMP7gwKKUYOCv4OET1N8uJrQ@mail.gmail.com> (raw)
In-Reply-To: <20110616072452.GA15366@elte.hu>
On Thu, Jun 16, 2011 at 8:24 AM, Ingo Molnar <mingo@elte.hu> wrote:
> - executing AIO in the vcpu thread eats up precious vcpu execution
> time: combined QCOW2 throughput would be limited by a single
> core's performance, and any time spent on QCOW2 processing would
> not be spent running the guest CPU. (In such a model we certainly
> couldnt do more intelligent, CPU-intense storage solutions like on
> the fly compress/decompress of QCOW2 data.)
This has been a problem in qemu-kvm. io_submit(2) steals time from
the guest (I think it was around 20us on the system I measured last
year).
Add the fact that the guest kernel might be holding a spinlock and it
becomes a scalability problem for SMP guests.
Anything that takes noticable CPU time should be done outside the vcpu thread.
Stefan
next prev parent reply other threads:[~2011-06-16 9:09 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-15 15:53 [ANNOUNCE] Native Linux KVM tool v2 Pekka Enberg
2011-06-15 16:30 ` Avi Kivity
2011-06-15 17:10 ` Pekka Enberg
2011-06-15 20:13 ` Prasad Joshi
2011-06-15 20:23 ` Sasha Levin
2011-06-15 20:49 ` Prasad Joshi
2011-06-15 21:53 ` Anthony Liguori
2011-06-15 22:04 ` Anthony Liguori
2011-06-15 22:07 ` Alexander Graf
2011-06-15 22:20 ` Anthony Liguori
2011-06-15 22:44 ` Anthony Liguori
2011-06-16 5:41 ` Pekka Enberg
2011-06-16 6:21 ` Pekka Enberg
2011-06-16 9:24 ` Christoph Hellwig
2011-06-16 9:34 ` Pekka Enberg
2011-06-16 9:48 ` Christoph Hellwig
2011-06-16 9:57 ` Ingo Molnar
2011-06-16 9:57 ` Pekka Enberg
2011-06-16 10:02 ` Christoph Hellwig
2011-06-16 11:22 ` Ingo Molnar
2011-06-16 11:25 ` Christoph Hellwig
2011-06-16 11:40 ` Ingo Molnar
2011-06-16 11:51 ` Christoph Hellwig
2011-06-17 7:21 ` Jeff Garzik
2011-06-16 5:45 ` Pekka Enberg
2011-06-16 7:24 ` Ingo Molnar
2011-06-16 7:33 ` Pekka Enberg
2011-06-16 8:07 ` Ingo Molnar
2011-06-16 9:09 ` Stefan Hajnoczi [this message]
2011-06-16 5:29 ` Stefan Hajnoczi
2011-06-16 5:42 ` Pekka Enberg
2011-06-15 21:41 ` Anthony Liguori
2011-06-16 14:28 ` Michael S. Tsirkin
2011-06-16 15:01 ` Asias He
2011-06-19 8:15 ` Michael S. Tsirkin
2011-06-16 14:48 ` Pekka Enberg
2011-06-16 22:50 ` Anthony Liguori
2011-06-17 1:03 ` Sasha Levin
2011-06-17 5:00 ` Stefan Hajnoczi
2011-06-17 13:41 ` Sasha Levin
2011-06-17 13:45 ` Anthony Liguori
2011-06-17 5:11 ` Stefan Hajnoczi
2011-06-17 7:31 ` justin
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