From: Paolo Bonzini <pbonzini@redhat.com>
To: Ming Lei <tom.leiming@gmail.com>, Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2
Date: Tue, 01 Jul 2014 18:49:30 +0200 [thread overview]
Message-ID: <53B2E69A.1090707@redhat.com> (raw)
In-Reply-To: <CACVXFVMfD_i-T+R-SiQkcZseEOhBzqDLG2eu0+hZOQawnDa1mw@mail.gmail.com>
Il 01/07/2014 16:49, Ming Lei ha scritto:
> Let me provide some data when running randread(bs 4k, libaio)
> from VM for 10sec:
>
> 1), qemu.git/master
> - write(): 731K
> - rt_sigprocmask(): 417K
> - read(): 21K
> - ppoll(): 10K
> - io_submit(): 5K
> - io_getevents(): 4K
>
> 2), qemu 2.0
> - write(): 9K
> - read(): 28K
> - ppoll(): 16K
> - io_submit(): 12K
> - io_getevents(): 10K
>
>> > The sigprocmask can probably be optimized away since the thread's
>> > signal mask remains unchanged most of the time.
>> >
>> > I'm not sure what is causing the write().
> I am investigating it...
I would guess sigprocmask is getcontext (from qemu_coroutine_new) and
write is aio_notify (from qemu_bh_schedule).
Both can be eliminated by introducing a fast path in
bdrv_aio_{read,write}v, that bypasses coroutines in the common case of
no I/O throttling, no copy-on-write, etc.
Paolo
next prev parent reply other threads:[~2014-07-01 16:49 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-26 15:14 [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2 Ming Lei
2014-06-26 15:29 ` Paolo Bonzini
2014-06-26 15:37 ` Ming Lei
2014-06-26 15:43 ` Paolo Bonzini
2014-06-26 15:47 ` Ming Lei
2014-06-26 15:57 ` Paolo Bonzini
2014-06-27 1:15 ` Ming Lei
2014-06-27 4:59 ` Paolo Bonzini
2014-06-27 6:23 ` Kevin Wolf
2014-06-27 7:35 ` Paolo Bonzini
2014-06-27 12:35 ` Ming Lei
2014-06-27 7:57 ` Ming Lei
2014-06-27 12:01 ` Stefan Hajnoczi
2014-06-27 12:21 ` Kevin Wolf
2014-06-27 14:50 ` Stefan Hajnoczi
2014-06-27 18:01 ` Ming Lei
2014-06-27 21:51 ` Paolo Bonzini
2014-06-28 9:58 ` Ming Lei
2014-06-30 8:08 ` Stefan Hajnoczi
2014-06-30 8:27 ` Ming Lei
2014-07-01 13:53 ` Ming Lei
2014-07-01 14:31 ` Stefan Hajnoczi
2014-07-01 14:49 ` Ming Lei
2014-07-01 16:49 ` Paolo Bonzini [this message]
2014-07-02 0:48 ` Ming Lei
2014-07-02 8:54 ` Stefan Hajnoczi
2014-07-02 9:13 ` Paolo Bonzini
2014-07-02 9:39 ` Kevin Wolf
2014-07-02 9:48 ` Paolo Bonzini
2014-07-02 10:01 ` Kevin Wolf
2014-07-02 10:23 ` Paolo Bonzini
2014-07-02 15:45 ` Ming Lei
2014-07-02 16:13 ` Ming Lei
2014-07-02 16:23 ` Paolo Bonzini
2014-07-02 16:27 ` Ming Lei
2014-07-02 16:38 ` Paolo Bonzini
2014-07-02 16:41 ` Ming Lei
2014-07-02 16:21 ` Paolo Bonzini
2014-07-03 4:54 ` Ming Lei
2014-07-03 10:29 ` Paolo Bonzini
2014-07-03 11:50 ` Ming Lei
2014-07-03 11:56 ` Paolo Bonzini
2014-07-03 12:09 ` Ming Lei
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