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Re: [Qemu-devel] [PATCH] Use qemu_eventfd for POSIX AIO

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH] Use qemu_eventfd for POSIX AIO
Date: Tue, 27 Sep 2011 17:42:17 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2

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

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