From: David Miller <davem@davemloft.net>
To: jarkao2@gmail.com
Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org
Subject: Re: [PATCH net-next-2.6] net: pskb_expand_head() optimization
Date: Mon, 20 Sep 2010 09:59:20 -0700 (PDT) [thread overview]
Message-ID: <20100920.095920.52212843.davem@davemloft.net> (raw)
In-Reply-To: <20100920072149.GA6353@ff.dom.local>
From: Jarek Poplawski <jarkao2@gmail.com>
Date: Mon, 20 Sep 2010 07:21:49 +0000
> On Sun, Sep 19, 2010 at 05:17:25PM -0700, David Miller wrote:
>> We definitely don't use frag lists for performance, if you look
>> in the GRO history the GRO code specifically has been changed
>> to prefer accumulating into the page vector whenever possible
>> because using frag lists is a lot slower.
>
> Yes, and GRO made frag lists more popular btw.
Yes. However, realize that this is only really a legacy from
inet_lro.
These drivers could restructure themselves to operate on pages.
I am pretty sure the hardware would be amicable to this and it
would likely improve performance just as favoring page vector
accumulation did for GRO.
> Btw, I wonder what is the exact reason we can't use only
> NET_SKBUFF_DATA_USES_OFFSET?
As Eric explained, and then demonstrated, it generates a non-trivial
increased amount of code.
This is almost certainly why Arnaldo didn't make it unconditional
back when he implemented the SKB data offset changes for 64-bit.
In my opinion, this duality of SKB pointer handling never causes
real problems because any change mistakenly accessing the pointers
directly usually gets caught by the first person who builds it on
64-bit :-)
next prev parent reply other threads:[~2010-09-20 16:59 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-03 3:43 [PATCH] net: Frag list lost on head expansion David Miller
2010-09-03 5:48 ` Eric Dumazet
2010-09-03 6:19 ` Eric Dumazet
2010-09-03 9:09 ` [PATCH net-next-2.6] net: pskb_expand_head() optimization Eric Dumazet
2010-09-03 13:46 ` David Miller
2010-09-07 2:20 ` David Miller
2010-09-07 5:02 ` Eric Dumazet
2010-09-07 5:05 ` David Miller
2010-09-07 9:16 ` Jarek Poplawski
2010-09-07 9:37 ` Eric Dumazet
2010-09-10 19:54 ` David Miller
2010-09-11 12:31 ` Jarek Poplawski
2010-09-12 3:30 ` David Miller
2010-09-12 10:45 ` Jarek Poplawski
2010-09-12 10:58 ` Jarek Poplawski
2010-09-12 15:58 ` David Miller
2010-09-12 16:13 ` David Miller
2010-09-12 20:57 ` Jarek Poplawski
2010-09-12 22:08 ` David Miller
2010-09-13 7:49 ` Jarek Poplawski
2010-09-12 19:55 ` Ben Pfaff
2010-09-12 20:24 ` David Miller
2010-09-12 20:45 ` Jarek Poplawski
2010-09-20 0:17 ` David Miller
2010-09-20 7:21 ` Jarek Poplawski
2010-09-20 9:02 ` Eric Dumazet
2010-09-20 9:14 ` Jarek Poplawski
2010-09-20 12:12 ` Jarek Poplawski
2010-09-20 12:40 ` Eric Dumazet
2010-09-20 16:59 ` David Miller [this message]
2010-09-07 1:25 ` David Miller
-- strict thread matches above, loose matches on Subject: below --
2010-07-22 19:12 [PATCH] Fix corruption of skb csum field in pskb_expand_head() of net/core/skbuff.c Andrea Shepard
2010-07-23 5:09 ` [PATCH net-next-2.6] net: pskb_expand_head() optimization Eric Dumazet
2010-07-25 4:06 ` David Miller
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