linux-kernel - Re: [RFC PATCH net-next] tun: support retrieving multiple packets in a single read with IFF_MULTI

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Message-ID: <20141222120957.GA21319@gondor.apana.org.au>
Date:	Mon, 22 Dec 2014 23:09:57 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Alex Gartrell <agartrell@...com>
Cc:	jasonwang@...hat.com, davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com,
	herbert@...dor.apena.org.au, kernel-team@...com, agartrell@...com
Subject: Re: [RFC PATCH net-next] tun: support retrieving multiple packets in
 a single read with IFF_MULTI_READ

Alex Gartrell <agartrell@...com> wrote:
> This patch adds the IFF_MULTI_READ flag.  This has the following behavior.
> 
> 1) If a read is too short for a packet, a single stripped packet will be read
> 
> 2) If a read is long enough for multiple packets, as many *full* packets
> will be read as possible.  We will not return a stripped packet, so even if
> there are many, many packets, we may get a short read.
> 
> In casual performance testing with a simple test program that simply reads
> and counts packets, IFF_MULTI_READ conservatively yielded a 30% CPU win, as
> measured by top.  Load was being driven by a bunch of hpings running on a
> server on the same L2 network (single hop through a top-of-rack switch).
> 
> Signed-off-by: Alex Gartrell <agartrell@...com>

As tun already has a socket interface can we do this through
recvmmsg?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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