From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D5F5C4320A for ; Wed, 1 Sep 2021 10:52:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D45561058 for ; Wed, 1 Sep 2021 10:52:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238741AbhIAKxH (ORCPT ); Wed, 1 Sep 2021 06:53:07 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:57065 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237715AbhIAKxG (ORCPT ); Wed, 1 Sep 2021 06:53:06 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630493529; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lm4mR3JYlL5ip2He+sEf0zphXUTsvwT6BkT7jCH1eyc=; b=ZGVYoHmBsTYdlDbrUdJjEQNfL0+FMnTEaJ/rUTjrxrO5he+3J/tfaDsKwJXSqaq/hsLIj6 AvzohNT1vQEcbN0GWEec/AQl2EAVuFa+LT5lE1cSo0tXXuZIjC12DqEWq61stgTxqbHMrh bo+7HBtr9ip712BjNkDxcv9I3QoVgL8= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-249-vW96852BMSqDtf-BqzRwfA-1; Wed, 01 Sep 2021 06:52:08 -0400 X-MC-Unique: vW96852BMSqDtf-BqzRwfA-1 Received: by mail-wr1-f72.google.com with SMTP id r17-20020adfda510000b02901526f76d738so677527wrl.0 for ; Wed, 01 Sep 2021 03:52:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=lm4mR3JYlL5ip2He+sEf0zphXUTsvwT6BkT7jCH1eyc=; b=GEBuCxTrN13bnJBWvPaYcmz/pS9v01X/1GmkrdxgWC355NhYK70F2miM7itvQox44C dhq26OCZ5PWb49Uhvuq2B35foSJPNyD3gLMq3Ho85KpPMNU+DYgbCRHVYM2opJzltfXV tkf/K/2We83IPGemKsNpPovzYjt1y5qWRn+h0U7L53BfJLZZSVp708N7VX7H5yjpk2U4 d1TZedoOY2Dnv1mkZhJ31uXtXGQ0mq1rREjrOM0wvYBsASfrj/3q79VAAe+BVVyZ+ow2 bG31SX+/sNlhV3naUyBltT5vVfdi0wzZqoMA6KKp0Q3GGmE2DUWPAZNBI6+S6xk/T6iF Pk2g== X-Gm-Message-State: AOAM530vsI1VovxUfRw8LramgSFrIKT/BUfi/+zsyxFiiArtm1E9W8ed f+h0/c4k8ScrlBsnbbfA/6w8Vbrs0WOp+z+Sz1bJVu/gIYMbIScsaK2RN4Tdt4a/1TQr0FldLXZ MEZt+Y2fTtSo5L8ARvbDRB3xI X-Received: by 2002:a05:6000:1081:: with SMTP id y1mr35464985wrw.415.1630493526918; Wed, 01 Sep 2021 03:52:06 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwyAY00ddiyzLDaqJY4HYxreDLtYrqdI7O3mR8VxvpDttJ01uAFBJixyKRBDKpoz3ljAanyXg== X-Received: by 2002:a05:6000:1081:: with SMTP id y1mr35464967wrw.415.1630493526747; Wed, 01 Sep 2021 03:52:06 -0700 (PDT) Received: from gerbillo.redhat.com (146-241-233-185.dyn.eolo.it. [146.241.233.185]) by smtp.gmail.com with ESMTPSA id a10sm4932882wmj.44.2021.09.01.03.52.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Sep 2021 03:52:06 -0700 (PDT) Message-ID: <9c9ef2228dfcb950b5c75382bd421c6169e547a0.camel@redhat.com> Subject: Re: [PATCH net-next] tcp: add tcp_tx_skb_cache_key checking in sk_stream_alloc_skb() From: Paolo Abeni To: Yunsheng Lin , davem@davemloft.net, kuba@kernel.org, MPTCP Upstream Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linuxarm@openeuler.org, edumazet@google.com, yoshfuji@linux-ipv6.org, dsahern@kernel.org Date: Wed, 01 Sep 2021 12:52:05 +0200 In-Reply-To: <1630492744-60396-1-git-send-email-linyunsheng@huawei.com> References: <1630492744-60396-1-git-send-email-linyunsheng@huawei.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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