netdev - Re: [PATCH 2/2] tun: fallback if skb

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Message-ID: <20080812101409.GA22114@gondor.apana.org.au>
Date:	Tue, 12 Aug 2008 18:14:09 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	netdev@...r.kernel.org, Max Krasnyansky <maxk@...lcomm.com>
Subject: Re: [PATCH 2/2] tun: fallback if skb_alloc() fails on big packets

On Tue, Aug 12, 2008 at 04:25:53PM +1000, Rusty Russell wrote:
> skb_alloc produces linear packets (using kmalloc()).  That can fail,
> so should we fall back to making paged skbs.
> 
> My original version of this patch always allocate paged skbs for big
> packets.  But that made performance drop from 8.4 seconds to 8.8
> seconds on 1G lguest->Host TCP xmit.  So now we only do that as a
> fallback.
> 
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

I'm not sure that this is really a good idea.  If anything then
tries to expand the head of this skb, they may fail and be forced
to drop the packet.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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