netdev - Re: [PATCH net-next v2] tcp: use tcp_flags in tcp_data

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Message-ID: <1411564948.15395.31.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 24 Sep 2014 06:22:28 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Weiping Pan <panweiping3@...il.com>
Cc:	netdev@...r.kernel.org, edumazet@...gle.com
Subject: Re: [PATCH net-next v2] tcp: use tcp_flags in tcp_data_queue()

On Wed, 2014-09-24 at 20:42 +0800, Weiping Pan wrote:
> Follow the idea in commit e11ecddf5128 (tcp: use TCP_SKB_CB(skb)->tcp_flags in
> input path), we can use tcp_flags to avoid cache miss.
> 

Well, there is no cache miss here. Lets try to have precise changelogs.

We access tcp_hdr(skb)->doff right before, so the tcp header is in cpu
cache.

So this patch is a cleanup and a way to help compiler to reduce register
pressure since skb->cb[] access is fast (skb is probably in a register)

Thanks.


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