Re: [PATCH 6/6] vhost_net: don't poll on -EFAULT

From: Jason Wang
Date: Mon Apr 16 2012 - 23:27:08 EST

On 04/16/2012 09:39 PM, Michael S. Tsirkin wrote:
On Mon, Apr 16, 2012 at 04:28:10PM +0800, Jason Wang wrote:
> On 04/16/2012 03:16 PM, Michael S. Tsirkin wrote:
> >On Mon, Apr 16, 2012 at 02:08:33PM +0800, Jason Wang wrote:
> >>Currently, we restart tx polling unconditionally when sendmsg()
> >>fails. This would cause unnecessary wakeups of vhost wokers as it's
> >>only needed when the socket send buffer were exceeded.
> >Why is this a problem?
> > This issue is when guest driver is able to hit the -EFAULT, vhost
> discard the the descriptor and restart the polling. This would wake
> vhost thread and repeat the loop again which waste cpu.
Does same thing happen if we get an error from copy from user?

Right, so do you think it makes sense that we only restart polling on -EAGAIN or -ENOBUFS?
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