From: Paolo Bonzini <pbonzini@redhat.com>
To: liu ping fan <qemulist@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Alex Bligh <alex@alex.org.uk>,
Jan Kiszka <jan.kiszka@siemens.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
qemu-devel@nongnu.org, Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff
Date: Wed, 24 Jul 2013 09:54:57 +0200 [thread overview]
Message-ID: <51EF8851.4040209@redhat.com> (raw)
In-Reply-To: <CAJnKYQmHA7Nwk8QsymNMF1bOeYxasHs+hZ0HoKg3a=rYE3GSjA@mail.gmail.com>
Il 24/07/2013 09:43, liu ping fan ha scritto:
> Paid some time to dig the kernel code, and find out that the
> resolution lost by timeout of poll/select..etc is cause by the timeout
> is a slack region.
> See code in
> do_poll()
> if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
>
> Notice the slack param, it causes the lose of resolution.
> The process default slack time inherits from init_task and it is
> .timer_slack_ns = 50000, /* 50 usec default slack */
> But we can fix it by PR_SET_TIMERSLACK to decrease it for select/poll/...
Right, good catch. I just learnt about PR_SET_TIMERSLACK. :)
Alex, can you add it to your series? (Note that you must set a timer
slack of 1, because 0 is interpreted as "default").
> So ppoll with timerslack adjustment will meet our requirement. But
> what about other non-linux system?
They might have their own mechanism similar to PR_SET_TIMERSLACK.
Paolo
next prev parent reply other threads:[~2013-07-24 7:55 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-21 8:42 [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff Liu Ping Fan
2013-07-21 8:42 ` [Qemu-devel] [RFC 1/8] timer: associate alarm_timer with AioContext Liu Ping Fan
2013-07-22 6:55 ` Jan Kiszka
2013-07-21 8:42 ` [Qemu-devel] [RFC 2/8] timer: pick out timer list info from QemuClock Liu Ping Fan
2013-07-21 8:43 ` [Qemu-devel] [RFC 3/8] timer: make timers_state static Liu Ping Fan
2013-07-22 6:36 ` [Qemu-trivial] " Jan Kiszka
2013-07-22 6:36 ` [Qemu-devel] " Jan Kiszka
2013-07-22 17:40 ` [Qemu-trivial] " Michael Tokarev
2013-07-22 17:40 ` [Qemu-devel] " Michael Tokarev
2013-07-21 8:43 ` [Qemu-devel] [RFC 4/8] timer: protect timers_state with lock Liu Ping Fan
2013-07-22 6:40 ` Jan Kiszka
2013-07-21 8:43 ` [Qemu-devel] [RFC 5/8] timer: associate timer with AioContext Liu Ping Fan
2013-07-21 8:43 ` [Qemu-devel] [RFC 6/8] timer: run timers on aio_poll Liu Ping Fan
2013-07-21 9:55 ` Alex Bligh
2013-07-23 2:56 ` liu ping fan
2013-07-23 14:22 ` Alex Bligh
2013-07-21 8:43 ` [Qemu-devel] [RFC 7/8] block: associate BlockDriverState with AioContext Liu Ping Fan
2013-07-21 8:43 ` [Qemu-devel] [RFC 8/8] block: enable throttle with aiocontext Liu Ping Fan
2013-07-21 9:53 ` [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff Alex Bligh
2013-07-22 4:38 ` liu ping fan
2013-07-22 6:28 ` Jan Kiszka
2013-07-23 2:51 ` liu ping fan
2013-07-25 11:44 ` Stefan Hajnoczi
2013-07-25 12:01 ` Jan Kiszka
2013-07-22 9:40 ` Alex Bligh
2013-07-22 10:18 ` liu ping fan
2013-07-23 2:53 ` liu ping fan
2013-07-23 10:30 ` Paolo Bonzini
2013-07-24 1:28 ` liu ping fan
2013-07-24 6:42 ` Paolo Bonzini
2013-07-24 7:31 ` Alex Bligh
2013-07-24 7:43 ` Paolo Bonzini
2013-07-24 8:01 ` Alex Bligh
2013-07-24 8:19 ` Paolo Bonzini
2013-07-24 8:37 ` Alex Bligh
2013-07-24 11:28 ` Paolo Bonzini
2013-07-24 8:30 ` liu ping fan
2013-07-24 7:43 ` liu ping fan
2013-07-24 7:54 ` Paolo Bonzini [this message]
2013-07-24 8:06 ` Alex Bligh
2013-07-24 14:46 ` [Qemu-devel] [PATCHv2a] [RFC 8/7 (really)] Add prctl(PR_SET_TIMERSLACK, 1, ...) to reduce timer slack Alex Bligh
2013-07-23 14:21 ` [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff Alex Bligh
2013-07-25 11:47 ` Stefan Hajnoczi
2013-07-25 12:05 ` Stefan Hajnoczi
2013-07-25 12:21 ` Alex Bligh
2013-07-25 12:32 ` Jan Kiszka
2013-07-25 12:35 ` Paolo Bonzini
2013-07-25 12:38 ` Jan Kiszka
2013-07-25 12:41 ` Stefan Hajnoczi
2013-07-25 12:48 ` Jan Kiszka
2013-07-25 13:02 ` Paolo Bonzini
2013-07-25 13:06 ` Jan Kiszka
2013-07-25 13:31 ` Stefan Hajnoczi
2013-07-25 14:01 ` Jan Kiszka
2013-07-25 12:59 ` Paolo Bonzini
2013-07-25 18:53 ` Alex Bligh
2013-07-26 8:43 ` Stefan Hajnoczi
2013-07-26 9:08 ` Alex Bligh
2013-07-26 9:19 ` Paolo Bonzini
2013-07-29 8:58 ` Kevin Wolf
2013-07-29 10:22 ` Alex Bligh
2013-07-29 10:45 ` Paolo Bonzini
2013-07-31 9:02 ` Stefan Hajnoczi
2013-07-26 10:05 ` Jan Kiszka
2013-07-26 19:29 ` Alex Bligh
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