From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Anthony Liguori <aliguori@us.ibm.com>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] Use qemu_eventfd for POSIX AIO
Date: Tue, 27 Sep 2011 17:42:17 +0300 [thread overview]
Message-ID: <4E81E0C9.7030702@redhat.com> (raw)
In-Reply-To: <4E81DF7C.4080403@siemens.com>
On 09/27/2011 05:36 PM, Jan Kiszka wrote:
> On 2011-09-27 16:34, Avi Kivity wrote:
> > On 09/27/2011 05:29 PM, Jan Kiszka wrote:
> >>>
> >>> Moreover, the eventfd() counter is not lossy (practically speaking) whereas if
> >>> you use pipe() as a counter, it will be lossy in practice.
> >>>
> >>> This is why posix aio uses pipe() and not eventfd().
> >>
> >> I don't get this yet. eventfd is lossy by default. It only decreases the
> >> counter on read if you specify EFD_SEMAPHORE - which we do not do.
> >>
> >
> > It's not lossy - a read returns the number of events written since the
> > last read.
>
> Yeah, but what's the point? We don't evaluate this.
>
>
If we write an interface that looks like eventfd but subtly differs,
someone will get bitten. If we write a new interface and implement it
via eventfd (or a pipe), no one gets bitten.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-09-27 14:42 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4E78C42D.5030207@siemens.com>
[not found] ` <20110921080600.GA9847@stefanha-thinkpad.localdomain>
[not found] ` <4E80B50B.9000301@siemens.com>
[not found] ` <4E80B55F.5020203@redhat.com>
[not found] ` <4E80BFF3.8000907@us.ibm.com>
[not found] ` <4E8190BE.3000801@redhat.com>
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 [this message]
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
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