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From: Rusty Russell <rusty@rustcorp.com.au>
To: David Miller <davem@davemloft.net>
Cc: virtualization@lists.linux-foundation.org,
	herbert@gondor.apana.org.au, virtualization@lists.osdl.org,
	netdev@vger.kernel.org
Subject: Re: [6/6] [VIRTIO] net: Allow receiving SG packets
Date: Tue, 22 Apr 2008 12:50:27 +1000	[thread overview]
Message-ID: <200804221250.27909.rusty@rustcorp.com.au> (raw)
In-Reply-To: <20080421.130418.01258045.davem@davemloft.net>

On Tuesday 22 April 2008 06:04:18 David Miller wrote:
> From: Rusty Russell <rusty@rustcorp.com.au>
> Date: Tue, 22 Apr 2008 05:06:16 +1000
>
> > I'm not sure what the right number is here.  Say worst case is header
> > which goes over a page boundary then MAX_SKB_FRAGS in the skb, but for
> > some reason that already has a +2:
> >
> > /* To allow 64K frame to be packed as single skb without frag_list */
> > #define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2)
> >
> > Unless someone explains, I'll change the xmit sg to 2+MAX_SKB_FRAGS as
> > well.
>
> MAX_SKB_FRAGS + 1 is what you ought to need.

Right, and so that's +2 for virtio_net because we have an extra header as  
Herbert points out.

But I was curious as to why the +2 in the MAX_SKB_FRAGS definition?

Thanks,
Rusty.

  parent reply	other threads:[~2008-04-22  2:50 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-18  3:12 [0/6] [NET]: virtio SG/TSO patches Herbert Xu
2008-04-18  3:14 ` [1/6] [TUN]: Add GSO support Herbert Xu
2008-04-18  3:15   ` [2/6] [TUN]: Add GSO detection Herbert Xu
2008-04-18  3:17     ` [3/6] [TUN]: Fix GSO mapping Herbert Xu
2008-04-18  3:19       ` [4/6] [KVM] virtio-net: Add SG/GSO support Herbert Xu
2008-04-18  3:21         ` [5/6] [VIRTIO] net: Add ethtool ops for SG/GSO Herbert Xu
2008-04-18  3:24           ` [6/6] [VIRTIO] net: Allow receiving SG packets Herbert Xu
2008-04-18 14:08             ` Rusty Russell
2008-04-18 14:30               ` Herbert Xu
2008-04-21 19:06             ` Rusty Russell
2008-04-21 20:04               ` David Miller
2008-04-22  1:13                 ` Herbert Xu
2008-04-22  2:50                 ` Rusty Russell [this message]
2008-04-22  2:55                   ` David Miller
2008-04-21 19:01           ` [5/6] [VIRTIO] net: Add ethtool ops for SG/GSO Rusty Russell
2008-04-22  1:15             ` Herbert Xu
2008-04-22  2:44               ` Rusty Russell
2008-05-29 10:32       ` [3/6] [TUN]: Fix GSO mapping Mark McLoughlin
2008-05-29 10:38         ` Herbert Xu

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