From: Avi Kivity <avi@redhat.com>
To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
Marcelo Tosatti <mtosatti@redhat.com>, kvm <kvm@vger.kernel.org>,
Kevin Wolf <kwolf@redhat.com>
Subject: Re: [PATCH] qemu-kvm: Switch POSIX compat AIO implementation to upstream
Date: Tue, 27 Sep 2011 12:00:46 +0300 [thread overview]
Message-ID: <4E8190BE.3000801@redhat.com> (raw)
In-Reply-To: <4E80BFF3.8000907@us.ibm.com>
On 09/26/2011 09:09 PM, Anthony Liguori wrote:
> On 09/26/2011 12:24 PM, Avi Kivity wrote:
>> On 09/26/2011 08:23 PM, Jan Kiszka wrote:
>>> >
>>> > Perhaps qemu_eventfd() can be used in the future instead of an
>>> explicit
>>> > pipe. Then Linux will do eventfd while other OSes will fall back to
>>> > pipes.
>>>
>>> Basically simpler code, or does this also have runtime benefits?
>>>
>>
>> In corner cases, the completion can block on the write() with pipes,
>> but not
>> eventfd.
>
> The pipe is O_NONBLOCK and the only thing the caller cares about is
> whether there is *some* data in the PIPE so it can happily ignore EAGAIN.
>
> So the pipe implementation never blocks on write() either. It may
> require multiple reads to drain the queue though whereas eventfd would
> only require a single read to drain the queue.
>
Oh, so switching to eventfd won't change much. Still nice though IMO.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-09-27 9:01 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-20 16:49 [PATCH] qemu-kvm: Switch POSIX compat AIO implementation to upstream Jan Kiszka
2011-09-21 8:06 ` Stefan Hajnoczi
2011-09-26 17:23 ` Jan Kiszka
2011-09-26 17:24 ` Avi Kivity
2011-09-26 18:09 ` Anthony Liguori
2011-09-27 9:00 ` Avi Kivity [this message]
2011-09-27 13:56 ` [Qemu-devel] [PATCH] Use qemu_eventfd for POSIX AIO Jan Kiszka
2011-09-27 14:07 ` Anthony Liguori
2011-09-27 14:11 ` Avi Kivity
2011-09-27 14:19 ` Anthony Liguori
2011-09-27 14:22 ` Avi Kivity
2011-09-27 14:22 ` Jan Kiszka
2011-09-27 14:38 ` Anthony Liguori
2011-09-27 14:29 ` Jan Kiszka
2011-09-27 14:34 ` Avi Kivity
2011-09-27 14:36 ` Jan Kiszka
2011-09-27 14:42 ` Avi Kivity
2011-09-27 14:45 ` Jan Kiszka
2011-09-27 14:48 ` Avi Kivity
2011-09-27 14:50 ` Jan Kiszka
2011-09-27 14:54 ` Avi Kivity
2011-09-27 14:57 ` Anthony Liguori
2011-09-27 14:59 ` Jan Kiszka
2011-09-27 14:36 ` Anthony Liguori
2011-09-27 14:41 ` Paolo Bonzini
2011-09-21 8:16 ` [PATCH] qemu-kvm: Switch POSIX compat AIO implementation to upstream Kevin Wolf
2011-09-26 16:56 ` Avi Kivity
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