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

[Jason Wang]

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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