From: "Jerry Chu" <hkchu@google.com>
To: "David Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Subject: Re: Socket buffer sizes with autotuning
Date: Wed, 7 May 2008 17:16:08 -0700 [thread overview]
Message-ID: <d1c2719f0805071716r1aa5ca71tc0da19296e0248e@mail.gmail.com> (raw)
In-Reply-To: <20080507.142013.219220793.davem@davemloft.net>
On Wed, May 7, 2008 at 2:20 PM, David Miller <davem@davemloft.net> wrote:
> From: "Jerry Chu" <hkchu@google.com>
> Date: Wed, 7 May 2008 11:54:01 -0700
>
>
> > This is one of many things about skb that I still don't completely understand.
> > Why in tcp_transmit_skb() we'll have to pskb_copy() if skb_cloned()?
>
> The other clone holder owns the packet header area. All packets on
> the retransmit queue of TCP are headerless. The call sites down
> into the device add the headers.
>
> Therefore we cannot have two paths modifying the headers at the same
> time.
Oh I see. I think I confused pskb_copy() with skb_copy() and kept thinking
why do we need to copy the whole thing...
>
>
> > Can't we clone a skb mulitple times? Is it due to some special optimization
> > from skb->fclone stuff... that imposes this restriction?
>
> No, it has nothing to do with fclone. It has to do with what instance
> owns the packet header area in front of the user's TCP data.
Thanks for explaining.
Jerry
>
next prev parent reply other threads:[~2008-05-08 0:16 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-23 23:29 Socket buffer sizes with autotuning Jerry Chu
2008-04-24 16:32 ` John Heffner
2008-04-25 0:49 ` Jerry Chu
2008-04-25 6:46 ` David Miller
2008-04-25 21:29 ` Jerry Chu
2008-04-25 21:35 ` David Miller
2008-04-28 18:30 ` Jerry Chu
2008-04-28 19:21 ` John Heffner
2008-04-28 20:44 ` Jerry Chu
2008-04-28 23:22 ` [PATCH 1/2] [NET]: Allow send-limited cwnd to grow up to max_burst when gso disabled John Heffner
2008-04-28 23:22 ` [PATCH 2/2] [NET]: Limit cwnd growth when deferring for GSO John Heffner
[not found] ` <d1c2719f0804281338j3984cf2bga31def0c2c1192a1@mail.gmail.com>
2008-04-28 23:28 ` Socket buffer sizes with autotuning John Heffner
2008-04-28 23:35 ` David Miller
2008-04-29 2:20 ` Jerry Chu
2008-04-25 7:05 ` David Miller
2008-05-07 3:57 ` Jerry Chu
2008-05-07 4:27 ` David Miller
2008-05-07 18:36 ` Jerry Chu
2008-05-07 21:18 ` David Miller
2008-05-08 1:37 ` Jerry Chu
2008-05-08 1:43 ` David Miller
2008-05-08 3:33 ` Jerry Chu
2008-05-12 22:22 ` Jerry Chu
2008-05-12 22:29 ` David Miller
2008-05-12 22:31 ` David Miller
2008-05-13 3:56 ` Jerry Chu
2008-05-13 3:58 ` David Miller
2008-05-13 4:00 ` Jerry Chu
2008-05-13 4:02 ` David Miller
2008-05-17 1:13 ` Jerry Chu
2008-05-17 1:29 ` David Miller
2008-05-17 1:47 ` Jerry Chu
2008-05-12 22:58 ` Jerry Chu
2008-05-12 23:01 ` David Miller
2008-05-07 4:28 ` David Miller
2008-05-07 18:54 ` Jerry Chu
2008-05-07 21:20 ` David Miller
2008-05-08 0:16 ` Jerry Chu [this message]
[not found] <d1c2719f0804241829s1bc3f41ejf7ebbff73ed96578@mail.gmail.com>
2008-04-25 7:06 ` Andi Kleen
2008-04-25 7:28 ` David Miller
2008-04-25 7:48 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2008-04-23 0:38 Rick Jones
2008-04-23 2:17 ` John Heffner
2008-04-23 3:59 ` David Miller
2008-04-23 16:32 ` Rick Jones
2008-04-23 16:58 ` John Heffner
2008-04-23 17:24 ` Rick Jones
2008-04-23 17:41 ` John Heffner
2008-04-23 17:46 ` Rick Jones
2008-04-24 22:21 ` Andi Kleen
2008-04-24 22:39 ` John Heffner
2008-04-25 1:28 ` David Miller
[not found] ` <65634d660804242234w66455bedve44801a98e3de9d9@mail.gmail.com>
2008-04-25 6:36 ` David Miller
2008-04-25 7:42 ` Tom Herbert
2008-04-25 7:46 ` David Miller
2008-04-28 17:51 ` Tom Herbert
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