On Tue, Apr 17, 2012 at 01:54:55PM +0800, Jason Wang wrote:On 04/17/2012 12:57 PM, Michael S. Tsirkin wrote:Yes but do you have a test that makes guest hit EFAULT or EINVAL?On Tue, Apr 17, 2012 at 11:27:01AM +0800, Jason Wang wrote:Not very hard, w/o this patch, we can see almost 100% cpuOn 04/16/2012 09:39 PM, Michael S. Tsirkin wrote:Sounds OK. BTW how do you test this?On Mon, Apr 16, 2012 at 04:28:10PM +0800, Jason Wang wrote:Right, so do you think it makes sense that we only restart pollingDoes same thing happen if we get an error from copy from user?On 04/16/2012 03:16 PM, Michael S. Tsirkin wrote:-EFAULT, vhost>On Mon, Apr 16, 2012 at 02:08:33PM +0800, Jason Wang wrote:> This issue is when guest driver is able to hit the>>Currently, we restart tx polling unconditionally when sendmsg()>Why is this a problem?
>>fails. This would cause unnecessary wakeups of vhost wokers as it's
>>only needed when the socket send buffer were exceeded.
discard the the descriptor and restart the polling. This would wake
vhost thread and repeat the loop again which waste cpu.
on -EAGAIN or -ENOBUFS?
utilization for vhost thread if guest hit EFAULT or EINVAL. With
this patch, the cpu utilization should be very low I think.
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