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From: David Miller <davem@davemloft.net>
To: rusty@rustcorp.com.au
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: Mon, 21 Apr 2008 19:55:21 -0700 (PDT)	[thread overview]
Message-ID: <20080421.195521.71448202.davem@davemloft.net> (raw)
In-Reply-To: <200804221250.27909.rusty@rustcorp.com.au>

From: Rusty Russell <rusty@rustcorp.com.au>
Date: Tue, 22 Apr 2008 12:50:27 +1000

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

To be honest I have no idea.

When Alexey added the TSO changeset way back then, it had the
"+2", from the history-2.6 tree:

commit 80223d5186f73bf42a7e260c66c9cb9f7d8ec9cf
Author: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Date:   Wed Aug 28 11:52:03 2002 -0700

    [NET]: Add TCP segmentation offload core infrastructure.

 ...
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a812681..9b6e6ad 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -109,7 +109,8 @@ struct sk_buff_head {
 
 struct sk_buff;
 
-#define MAX_SKB_FRAGS 6
+/* To allow 64K frame to be packed as single skb without frag_list */
+#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2)
 
 typedef struct skb_frag_struct skb_frag_t;
 

      reply	other threads:[~2008-04-22  2:55 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20080418031257.GA17993@gondor.apana.org.au>
     [not found] ` <20080418032142.GD18071@gondor.apana.org.au>
     [not found]   ` <20080418032427.GE18071@gondor.apana.org.au>
2008-04-21 19:06     ` [6/6] [VIRTIO] net: Allow receiving SG packets Rusty Russell
2008-04-21 20:04       ` David Miller
2008-04-22  1:13         ` Herbert Xu
2008-04-22  2:50         ` Rusty Russell
2008-04-22  2:55           ` David Miller [this message]

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