Linux Virtualization - Dec 2015 - [PATCH net-next 3/3] vhost_net: basic polling support

On 11/30/2015 06:44 PM, Michael S. Tsirkin wrote:
> On Wed, Nov 25, 2015 at 03:11:29PM +0800, Jason Wang wrote:
>> > This patch tries to poll for new added tx buffer or socket receive
>> > queue for a while at the end of tx/rx processing. The maximum time
>> > spent on polling were specified through a new kind of vring ioctl.
>> > 
>> > Signed-off-by: Jason Wang <jasowang at redhat.com>
> One further enhancement would be to actually poll
> the underlying device. This should be reasonably
> straight-forward with macvtap (especially in the
> passthrough mode).
>
>
Yes, it is. I have some patches to do this by replacing
skb_queue_empty() with sk_busy_loop() but for tap. Tests does not show
any improvement but some regression.  Maybe it's better to test macvtap.

On Tue, Dec 01, 2015 at 01:17:49PM +0800, Jason Wang
wrote:
> 
> 
> On 11/30/2015 06:44 PM, Michael S. Tsirkin wrote:
> > On Wed, Nov 25, 2015 at 03:11:29PM +0800, Jason Wang wrote:
> >> > This patch tries to poll for new added tx buffer or socket
receive
> >> > queue for a while at the end of tx/rx processing. The maximum
time
> >> > spent on polling were specified through a new kind of vring
ioctl.
> >> > 
> >> > Signed-off-by: Jason Wang <jasowang at redhat.com>
> > One further enhancement would be to actually poll
> > the underlying device. This should be reasonably
> > straight-forward with macvtap (especially in the
> > passthrough mode).
> >
> >
> 
> Yes, it is. I have some patches to do this by replacing
> skb_queue_empty() with sk_busy_loop() but for tap.
We probably don't want to do this unconditionally, though.
> Tests does not show
> any improvement but some regression.
Did you add code to call sk_mark_napi_id on tap then?
sk_busy_loop won't do anything useful without.
>  Maybe it's better to test macvtap.
Same thing ...

-- 
MST

On 12/01/2015 10:43 PM, Michael S. Tsirkin wrote:
> On Tue, Dec 01, 2015 at 01:17:49PM +0800, Jason Wang wrote:
>>
>> On 11/30/2015 06:44 PM, Michael S. Tsirkin wrote:
>>> On Wed, Nov 25, 2015 at 03:11:29PM +0800, Jason Wang wrote:
>>>>> This patch tries to poll for new added tx buffer or socket
receive
>>>>> queue for a while at the end of tx/rx processing. The
maximum time
>>>>> spent on polling were specified through a new kind of vring
ioctl.
>>>>>
>>>>> Signed-off-by: Jason Wang <jasowang at redhat.com>
>>> One further enhancement would be to actually poll
>>> the underlying device. This should be reasonably
>>> straight-forward with macvtap (especially in the
>>> passthrough mode).
>>>
>>>
>> Yes, it is. I have some patches to do this by replacing
>> skb_queue_empty() with sk_busy_loop() but for tap.
> We probably don't want to do this unconditionally, though.
>
>> Tests does not show
>> any improvement but some regression.
> Did you add code to call sk_mark_napi_id on tap then?
> sk_busy_loop won't do anything useful without.
Yes I did. Probably something wrong elsewhere.
>
>>  Maybe it's better to test macvtap.
> Same thing ...
>