netdev - Re: [PATCH net-next 3/3] vhost_net: basic polling support

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Date:	Fri, 4 Dec 2015 10:24:00 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] vhost_net: basic polling support



On 12/02/2015 08:36 PM, Michael S. Tsirkin wrote:
> On Wed, Dec 02, 2015 at 01:04:03PM +0800, Jason Wang wrote:
>>
>> 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@...hat.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.
> Is this for guest-to-guest?

Nope. Like you said below, since it requires NAPI so it was external
host to guest.

>  the patch to do napi
> for tap is still not upstream due to minor performance
> regression.  Want me to repost it?

Sure, I've played this a little bit in the past too.

>
>>>>  Maybe it's better to test macvtap.
>>> Same thing ...
>>>
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