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: Sun, 04 Apr 2010 19:58:02 +0300 [thread overview] Message-ID: <4BB8C51A.6070908@redhat.com> (raw) In-Reply-To: <201004041525.18211.paul@codesourcery.com> On 04/04/2010 05:25 PM, Paul Brook wrote: >>> Looks like the tablet is set to 100 Hz polling rate. We may be able >>> to get away with 30 Hz or even less (ep_bInterval, in ms, in >>> hw/usb-wacom.c). >>> >> Changing the USB tablet polling interval from 10ms to 100ms in both >> hw/usb-wacom.c and hw/usb-hid.c made no difference except the an increase >> in bInterval shown in lsusb -v in the guest and the hint of jerky mouse >> movement I expected from setting this value so high. A similar change to >> the polling interval for the keyboard and mouse also made no difference to >> their performance impact. >> > The USB HID devices implement the SET_IDLE command, so the polling interval > will have no real effect on performance. > On a Linux guest (F12), I see 125 USB interrupts per second with no mouse movement, so something is broken (on the guest or host). > My guess is that the overhead you're seeing is entirely from the USB host > adapter having to wake up and check the transport descriptor lists. This will > only result in the guest being woken if a device actually responds (as > mentioned above it should not). > A quick profile on the host side doesn't show this. Instead, I see a lot of select() overhead. Surprising as there are ~10 descriptors being polled, so ~1200 polls per second. Maybe epoll will help here. -- 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: Sun, 04 Apr 2010 19:58:02 +0300 [thread overview] Message-ID: <4BB8C51A.6070908@redhat.com> (raw) In-Reply-To: <201004041525.18211.paul@codesourcery.com> On 04/04/2010 05:25 PM, Paul Brook wrote: >>> Looks like the tablet is set to 100 Hz polling rate. We may be able >>> to get away with 30 Hz or even less (ep_bInterval, in ms, in >>> hw/usb-wacom.c). >>> >> Changing the USB tablet polling interval from 10ms to 100ms in both >> hw/usb-wacom.c and hw/usb-hid.c made no difference except the an increase >> in bInterval shown in lsusb -v in the guest and the hint of jerky mouse >> movement I expected from setting this value so high. A similar change to >> the polling interval for the keyboard and mouse also made no difference to >> their performance impact. >> > The USB HID devices implement the SET_IDLE command, so the polling interval > will have no real effect on performance. > On a Linux guest (F12), I see 125 USB interrupts per second with no mouse movement, so something is broken (on the guest or host). > My guess is that the overhead you're seeing is entirely from the USB host > adapter having to wake up and check the transport descriptor lists. This will > only result in the guest being woken if a device actually responds (as > mentioned above it should not). > A quick profile on the host side doesn't show this. Instead, I see a lot of select() overhead. Surprising as there are ~10 descriptors being polled, so ~1200 polls per second. Maybe epoll will help here. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2010-04-04 16:58 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 [this message] 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 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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