netdev - Re: something is wrong in commit 971f10eca1 - tcp: better TCP_SKB

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Date:	Wed, 15 Oct 2014 14:22:48 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Krzysztof Kolasa <kkolasa@...soft.pl>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...il.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: something is wrong in commit 971f10eca1 - tcp: better TCP_SKB_CB
 layout to reduce cache line misses

On Wed, Oct 15, 2014 at 1:42 PM, Krzysztof Kolasa <kkolasa@...soft.pl> wrote:
> W dniu 15.10.2014 o 22:36, Cong Wang pisze:
>>
>> On Wed, Oct 15, 2014 at 3:35 AM, Krzysztof Kolasa <kkolasa@...soft.pl>
>> wrote:
>>>
>>> one-line patch not resolve problem, fix created by Cong Wang resolves
>>> problem !!!
>>>
>>> tested on 64bit system and working OK
>>>
>> So my patch fixes your problem on 64bit but not on 32bit,
>> is this correct?
>
> Yes

Cool! Patches are coming.

Meanwhile Eric is debugging it, do you mind to try a followup quick
fix on your 32bit system?

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e13d778..12bd3f6 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1006,8 +1006,7 @@ static int tcp_transmit_skb(struct sock *sk,
struct sk_buff *skb, int clone_it,
        skb->tstamp.tv64 = 0;

        /* Cleanup our debris for IP stacks */
-       memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
-                              sizeof(struct inet6_skb_parm)));
+       memset(TCPCB(skb), 0, sizeof(*TCPCB(skb)));

        err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
--
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