From: Jarek Poplawski <jarkao2@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org
Subject: Re: [PATCH net-next-2.6] net: pskb_expand_head() optimization
Date: Sun, 12 Sep 2010 22:45:52 +0200 [thread overview]
Message-ID: <20100912204552.GA2585@del.dom.local> (raw)
In-Reply-To: <20100912.085833.226777368.davem@davemloft.net>
On Sun, Sep 12, 2010 at 08:58:33AM -0700, David Miller wrote:
> From: Jarek Poplawski <jarkao2@gmail.com>
> Date: Sun, 12 Sep 2010 12:45:34 +0200
>
> > Then a few more questions:
> > 1) if doubly linked lists really require such pskb_copying, isn't it
> > all too costly?
>
> In the common case the data reference will be one, so we will not
> copy.
Even if so, one such a case on the fast path should hit performance,
so it would need special reviewing.
>
> > 2) why skb_clone isn't enough instead of pskb_copy?
>
> Can't share the metadata.
I'd really like to understand why the change in handling next/prev
should affect more than skb pointers wrt. current sharing.
>
> > 3) since skb_clone has some cost too, why e.g. saving only the pointer
> > to the tail of the list in skb_shared_info isn't enough?
>
> Then we won't get the rest of the advantages of using list_head such
> as prefetching during traversals, automatic debugging facilities, et al.
Right, we need to sum pros and cons. So, what's the pros? ;-)
Jarek P.
next prev parent reply other threads:[~2010-09-12 20:45 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 [this message]
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
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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