linux-kernel - Re: [PATCH v5 0/2] skb_array: array based FIFO for skbs

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Date:	Mon, 30 May 2016 18:37:05 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>, davem@...emloft.net,
	netdev@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	brouer@...hat.com
Subject: Re: [PATCH v5 0/2] skb_array: array based FIFO for skbs

On Mon, May 30, 2016 at 05:59:33PM +0800, Jason Wang wrote:
> 
> 
> On 2016年05月23日 18:43, Michael S. Tsirkin wrote:
> >This is in response to the proposal by Jason to make tun
> >rx packet queue lockless using a circular buffer.
> >My testing seems to show that at least for the common usecase
> >in networking, which isn't lockless, circular buffer
> >with indices does not perform that well, because
> >each index access causes a cache line to bounce between
> >CPUs, and index access causes stalls due to the dependency.
> 
> I change tun to use skb array, looks like it can give about 5% more faster
> than skb ring.

OK and skb ring is 9% faster than the linked list, so together
this is a 14% speedup?

> And we usually don't need touch bhs during consume and produce (e.g for the
> case of tun).
> 
> Thanks

Maybe I'll drop it in v6 then ...
Could you post the full tun patchset please?

-- 
MST