Re: [Qemu-devel] Linux SIGIO handling changes

[Anthony Liguori]

Anders Melchiorsen wrote:
> I am resending this patch, split into two parts now.
>
> This cleans up SIGIO handling to improve latency:
> - SIGALRM for alarm timers
> - enable SIGIO on qemu_set_fd_handler2()
>
> The issue was found in KVM, where it is much more visible,
> because there is no periodic timer. However, it has been
> confirmed (by Aurelien Jarno) that even for qemu, this
> approach "improves network transfers in a huge way".
>
> Please apply, or give a firm rejection so I can stop resending.
>   

Probably the right thing to do is the direction KVM is moving toward, 
i.e. have a separate IO thread.

Setting SIGIO on every file descriptor is really just a hack to break 
out of the cpu exec loop.  It's unclear to me whether it's really always 
the right thing to do for every file descriptor.

Regards,

Anthony Liguori

> Cheers,
> Anders.
>
>
>
>