linux-kernel - Re: [PATCH RFC v4 net-next 0/5] virtio

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Date:	Tue, 2 Dec 2014 12:08:07 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	"'Jason Wang'" <jasowang@...hat.com>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"pagupta@...hat.com" <pagupta@...hat.com>
Subject: Re: [PATCH RFC v4 net-next 0/5] virtio_net: enabling tx interrupts

On Tue, Dec 02, 2014 at 10:00:06AM +0000, David Laight wrote:
> From: Jason Wang
> > > On Mon, Dec 01, 2014 at 06:17:03PM +0800, Jason Wang wrote:
> > >>  Hello:
> > >>
> > >>  We used to orphan packets before transmission for virtio-net. This
> > >> breaks
> > >>  socket accounting and can lead serveral functions won't work, e.g:
> > >>
> > >>  - Byte Queue Limit depends on tx completion nofication to work.
> > >>  - Packet Generator depends on tx completion nofication for the last
> > >>    transmitted packet to complete.
> > >>  - TCP Small Queue depends on proper accounting of sk_wmem_alloc to
> > >> work.
> > >>
> > >>  This series tries to solve the issue by enabling tx interrupts. To
> > >> minize
> > >>  the performance impacts of this, several optimizations were used:
> > >>
> > >>  - In guest side, virtqueue_enable_cb_delayed() was used to delay the tx
> > >>    interrupt untile 3/4 pending packets were sent.
> 
> Doesn't that give problems for intermittent transmits?
> 
> ...
> 
> 	David
> 

No because it has not effect in that case.

-- 
MST
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