From: Avi Kivity <avi@redhat.com>
To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org, "Chris Webb" <chris@arachsys.com>,
kvm@vger.kernel.org,
"Jernej Simončič" <jernej's-kvm@eternallybored.org>
Subject: Re: [Qemu-devel] High CPU use of -usbdevice tablet (was Re: KVM usability)
Date: Mon, 05 Apr 2010 11:22:32 +0300 [thread overview]
Message-ID: <4BB99DC8.6030106@redhat.com> (raw)
In-Reply-To: <201004042253.18066.paul@codesourcery.com>
On 04/05/2010 12:53 AM, Paul Brook wrote:
>
>> Surprising as there are ~10 descriptors being
>> polled, so ~1200 polls per second. Maybe epoll will help here.
>>
> I'm not sure where you get 1200 from. select will be called once per host
> wakeup. i.e. if the USB controller is enabled then 1k times per second due to
> the frame tick.
>
That was 125 interrupts/sec x 10 fds ('poll' here was the per-file
callback in the kernel, not the select call). With your numbers, it's
more like 10k polls/sec which can be eliminated.
> Are you sure there are actually 10 descriptors being polled? Remember that the
> nfds argument is the value of the largest fd in the set (+1), not the number
> of descriptors in the set.
>
I was estimating from the strace parsed output, the real number is 7.
So the kernel calls 7k callbacks/sec only to return with a timeout.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@redhat.com>
To: Paul Brook <paul@codesourcery.com>
Cc: "Chris Webb" <chris@arachsys.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
"Jernej Simončič" <jernej's-kvm@eternallybored.org>
Subject: Re: [Qemu-devel] High CPU use of -usbdevice tablet (was Re: KVM usability)
Date: Mon, 05 Apr 2010 11:22:32 +0300 [thread overview]
Message-ID: <4BB99DC8.6030106@redhat.com> (raw)
In-Reply-To: <201004042253.18066.paul@codesourcery.com>
On 04/05/2010 12:53 AM, Paul Brook wrote:
>
>> Surprising as there are ~10 descriptors being
>> polled, so ~1200 polls per second. Maybe epoll will help here.
>>
> I'm not sure where you get 1200 from. select will be called once per host
> wakeup. i.e. if the USB controller is enabled then 1k times per second due to
> the frame tick.
>
That was 125 interrupts/sec x 10 fds ('poll' here was the per-file
callback in the kernel, not the select call). With your numbers, it's
more like 10k polls/sec which can be eliminated.
> Are you sure there are actually 10 descriptors being polled? Remember that the
> nfds argument is the value of the largest fd in the set (+1), not the number
> of descriptors in the set.
>
I was estimating from the strace parsed output, the real number is 7.
So the kernel calls 7k callbacks/sec only to return with a timeout.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2010-04-05 8:23 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1267068445.1726.25.camel@localhost>
[not found] ` <1267089644.12790.74.camel@laptop>
2010-02-26 2:49 ` Enhance perf to support KVM Zhang, Yanmin
2010-02-26 9:01 ` Ingo Molnar
2010-02-26 9:53 ` Avi Kivity
2010-02-26 10:35 ` Ingo Molnar
2010-02-26 10:47 ` Avi Kivity
2010-02-26 11:17 ` Ingo Molnar
2010-02-26 11:44 ` Avi Kivity
2010-02-26 12:46 ` Ingo Molnar
2010-02-26 12:54 ` Avi Kivity
2010-02-26 13:16 ` Ingo Molnar
2010-02-26 13:57 ` Jes Sorensen
2010-02-26 14:04 ` Avi Kivity
2010-02-26 14:23 ` Ingo Molnar
2010-02-26 15:06 ` Avi Kivity
2010-03-02 16:46 ` Paolo Bonzini
2010-03-02 17:12 ` Arnaldo Carvalho de Melo
2010-03-02 17:20 ` Paolo Bonzini
2010-03-02 17:24 ` Ingo Molnar
2010-03-02 17:17 ` Ingo Molnar
2010-03-07 14:17 ` Avi Kivity
2010-02-26 18:33 ` Avi Kivity
2010-02-27 10:56 ` KVM usability Ingo Molnar
2010-02-27 13:30 ` Jan Kiszka
2010-02-27 13:30 ` [Qemu-devel] " Jan Kiszka
2010-02-27 14:48 ` Ian Kirk
2010-02-27 15:32 ` Zachary Amsden
2010-02-27 17:25 ` Ingo Molnar
2010-03-01 15:33 ` Anthony Liguori
2010-03-01 16:48 ` Zachary Amsden
2010-03-01 17:41 ` Arnaldo Carvalho de Melo
2010-03-01 18:29 ` Zachary Amsden
2010-03-01 20:56 ` Ingo Molnar
2010-03-01 21:45 ` Anthony Liguori
2010-03-01 22:06 ` Zachary Amsden
2010-03-02 0:33 ` Ingo Molnar
2010-03-02 0:30 ` Ingo Molnar
2010-03-02 2:34 ` Anthony Liguori
2010-03-02 8:39 ` Chris Webb
2010-03-07 18:42 ` Avi Kivity
2010-03-02 10:30 ` Ingo Molnar
2010-03-07 9:35 ` Avi Kivity
2010-03-07 9:56 ` Pekka Enberg
2010-03-07 10:11 ` Avi Kivity
2010-03-07 18:42 ` Ingo Molnar
2010-03-07 15:14 ` Luca Barbieri
2010-03-07 18:16 ` Avi Kivity
2010-03-07 18:01 ` Arnaldo Carvalho de Melo
2010-03-07 18:15 ` Avi Kivity
2010-03-07 18:53 ` Arnaldo Carvalho de Melo
2010-03-07 19:05 ` Avi Kivity
2010-03-07 18:25 ` Avi Kivity
2010-03-01 9:25 ` Ingo Molnar
2010-03-01 15:36 ` Anthony Liguori
2010-03-01 15:14 ` Anthony Liguori
2010-03-01 15:42 ` Daniel P. Berrange
2010-03-02 1:12 ` Dustin Kirkland
2010-03-02 10:11 ` Peter Zijlstra
2010-03-02 13:37 ` Nikolai K. Bochev
2010-03-02 14:22 ` Gerd Hoffmann
2010-03-02 14:29 ` Ingo Molnar
2010-03-07 9:22 ` Avi Kivity
2010-03-02 14:37 ` Daniel P. Berrange
2010-03-02 14:52 ` Gerd Hoffmann
2010-03-02 14:56 ` Daniel P. Berrange
2010-03-02 15:13 ` Gerd Hoffmann
2010-03-04 20:00 ` Lucas Meneghel Rodrigues
2010-03-04 20:13 ` Zachary Amsden
2010-03-04 20:34 ` Anthony Liguori
2010-03-04 22:23 ` H. Peter Anvin
2010-03-05 7:44 ` Markus Armbruster
2010-03-07 11:25 ` Avi Kivity
2010-03-01 21:12 ` Dustin Kirkland
2010-03-01 21:59 ` Anthony Liguori
2010-03-02 2:34 ` Alexander Graf
2010-03-02 2:36 ` Anthony Liguori
2010-03-09 13:32 ` Avi Kivity
2010-03-09 14:32 ` Dustin Kirkland
2010-03-09 14:38 ` Alexander Graf
2010-03-09 14:50 ` Anthony Liguori
2010-03-09 14:52 ` Avi Kivity
2010-03-09 14:57 ` Anthony Liguori
2010-03-09 17:11 ` Avi Kivity
2010-03-09 17:27 ` Anthony Liguori
2010-03-09 17:30 ` Avi Kivity
2010-03-09 14:49 ` Anthony Liguori
2010-03-09 14:54 ` Avi Kivity
2010-03-02 3:02 ` Dustin Kirkland
2010-03-02 8:21 ` Chris Webb
2010-03-02 14:54 ` Dustin Kirkland
[not found] ` <428008581.20100302103400@eternallybored.org>
2010-03-07 11:35 ` Avi Kivity
2010-04-04 12:31 ` High CPU use of -usbdevice tablet (was Re: KVM usability) Chris Webb
2010-04-04 12:31 ` [Qemu-devel] " Chris Webb
2010-04-04 14:25 ` Paul Brook
2010-04-04 14:25 ` Paul Brook
2010-04-04 16:58 ` Avi Kivity
2010-04-04 16:58 ` Avi Kivity
2010-04-04 21:03 ` Paul Brook
2010-04-04 21:03 ` Paul Brook
2010-04-04 21:53 ` Paul Brook
2010-04-04 21:53 ` Paul Brook
2010-04-05 8:22 ` Avi Kivity [this message]
2010-04-05 8:22 ` Avi Kivity
2010-03-03 2:57 ` KVM usability Ross Boylan
2010-03-03 8:55 ` Daniel P. Berrange
2010-03-03 15:42 ` Ross Boylan
2010-03-07 14:29 ` Avi Kivity
2010-02-26 11:48 ` Enhance perf to support KVM Peter Zijlstra
2010-02-26 11:53 ` Avi Kivity
2010-02-26 20:17 ` Anthony Liguori
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