Re: [kvm-devel] [patch 2/2] QEMU: decrease console "refresh rate" with -nographic

[Anthony L. <ali...@us...>]

Avi Kivity wrote:
> Anthony Liguori wrote:
>>
>> BTW, when we set O_ASYNC on the tap fd, we're eliminating 
>> O_NONBLOCK.  This means that we have to poll loop select() when 
>> readv()'ing packets instead of just reading until hitting AGAIN.  
>> This means at least an extra syscall per packet.
>
> I didn't know that O_ASYNC and O_NONBLOCK were mutually exclusive.  
> Can you point me at the relevant documentation?

I don't know that they are, but we're doing an:

fcntl(fd, F_SETFL, O_ASYNC);

F_SETFL is not additive so the previous O_NONBLOCK gets dropped.

Regards,

Anthony Liguori