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

[Jan Kiszka]

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.

Jan

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