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From: Paolo Abeni <pabeni@redhat.com>
To: Yunsheng Lin <linyunsheng@huawei.com>,
	davem@davemloft.net, kuba@kernel.org,
	MPTCP Upstream <mptcp@lists.linux.dev>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linuxarm@openeuler.org, edumazet@google.com,
	yoshfuji@linux-ipv6.org, dsahern@kernel.org
Subject: Re: [PATCH net-next] tcp: add tcp_tx_skb_cache_key checking in sk_stream_alloc_skb()
Date: Wed, 01 Sep 2021 12:52:05 +0200	[thread overview]
Message-ID: <9c9ef2228dfcb950b5c75382bd421c6169e547a0.camel@redhat.com> (raw)
In-Reply-To: <1630492744-60396-1-git-send-email-linyunsheng@huawei.com>

On Wed, 2021-09-01 at 18:39 +0800, Yunsheng Lin wrote:
> Since tcp_tx_skb_cache is disabled by default in:
> commit 0b7d7f6b2208 ("tcp: add tcp_tx_skb_cache sysctl")
> 
> Add tcp_tx_skb_cache_key checking in sk_stream_alloc_skb() to
> avoid possible branch-misses.
> 
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>

Note that MPTCP is currently exploiting sk->sk_tx_skb_cache. If we get
this patch goes in as-is, it will break mptcp.

One possible solution would be to let mptcp usage enable sk-
>sk_tx_skb_cache, but that has relevant side effects on plain TCP. 

Another options would be re-work once again the mptcp xmit path to
avoid using sk->sk_tx_skb_cache.

Cheers,

Paolo




  reply	other threads:[~2021-09-01 10:52 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-01 10:39 Yunsheng Lin
2021-09-01 10:52 ` Paolo Abeni [this message]
2021-09-01 15:06   ` Eric Dumazet
2021-09-01 15:16     ` Eric Dumazet
2021-09-01 15:25       ` Paolo Abeni
2021-09-01 15:29         ` Eric Dumazet
2021-09-01 16:01         ` Paolo Abeni
2021-09-01 16:02           ` Eric Dumazet
2021-09-02  0:47 ` Yunsheng Lin
2021-09-02  1:13   ` Eric Dumazet
2021-09-02  2:05     ` Yunsheng Lin

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