From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 79A3534A777 for ; Thu, 23 Oct 2025 17:43:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761241416; cv=none; b=PhC4RL5lo+3GYP2mE2qRl1fDo3HffjAb5z+D46Uq7f8O033TdJnDezIvfMtrIPS3jI9J1GFSvLtVSuZPX/gTv53mXH2LvQrV8FpxYwfropWQLh4X8Y39d68JdfexlnrYltuPwFkJ8MUb3ASoyZvGVGUEcZMBAl6dckRBWuwOHh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761241416; c=relaxed/simple; bh=x6pP27kZSEZ6+lrACdnnTVbaNxch+DTIW+n4R9zENC8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iR7Eih+F9LkMckcf5hrjxHoKpLgDYq61KfiGrDuGGk9uvB3M/ZkAly5v2O5LcQWktF3O45ikeDMxlYVNfzEsg8WOjhLvWjdOCP5HqFYIUx35cD4f9J16b4DACs7WzWN2RyADstORzNUYrxYJXpwIx3g7FP+nuXY4FjO5kz8WNzQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mBsi331R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mBsi331R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D366C4CEE7; Thu, 23 Oct 2025 17:43:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761241416; bh=x6pP27kZSEZ6+lrACdnnTVbaNxch+DTIW+n4R9zENC8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mBsi331RWB3r3Oc0+UFh9r7RMUzI1HFW2jDiGW8sTaUWx2Ts9s1tleU679AH+Wwsb 0f3Dc/dTjF5BbnpSJoL3NSYDQc0xNMVwS0ISt54h8RHGUu6yzfcKJHjsQmp/3On6T6 +N0wHU2AJoD+4qTNI38zN4XYk/yG9kl/Oh6QuEeJcujG0sGe+OPcWn/4ZTOvsLY+km VdCrwZOk/5zgLqsdcyxTAeHe3fTbRFrfl7s9dhYlp+o/6aN74LvcPvLn/BRAWuFHyS C8xiQ+vglbNhBVyCMw9fz0euJG6Acr9qJs64Y31HizNhT+qUy57Kf308KZYW5UGpaC cQJFvQl9dFiBA== Message-ID: <0d2669ee-4625-4551-96e9-22171a406f8c@kernel.org> Date: Thu, 23 Oct 2025 19:43:33 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 mptcp-next 11/11] mptcp: leverage the backlog for RX packet processing Content-Language: en-GB, fr-BE To: Mat Martineau , Paolo Abeni Cc: Geliang Tang , mptcp@lists.linux.dev References: <2201f259d2176bca0ad37500a352658f7ef5a1f0.1761142784.git.pabeni@redhat.com> <3feb8c2a-2098-4626-8bf2-edd66f679463@redhat.com> <34f90baa-72ff-4c00-917a-a0d65ff0e608@kernel.org> <4d70359f-20bb-4575-b6c5-8e862c2547e3@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Mat, Paolo, On 23/10/2025 19:02, Mat Martineau wrote: > On Thu, 23 Oct 2025, Matthieu Baerts wrote: > >> Hi Paolo, Mat, >> >> On 23/10/2025 17:11, Paolo Abeni wrote: >>> >>> >>> On 10/22/25 4:31 PM, Paolo Abeni wrote: >>>> When the msk socket is owned or the msk receive buffer is full, >>>> move the incoming skbs in a msk level backlog list. This avoid >>>> traversing the joined subflows and acquiring the subflow level >>>> socket lock at reception time, improving the RX performances. >>>> >>>> When processing the backlog, use the fwd alloc memory borrowed from >>>> the incoming subflow. skbs exceeding the msk receive space are >>>> not dropped; instead they are kept into the backlog until the receive >>>> buffer is freed. Dropping packets already acked at the TCP level is >>>> explicitly discouraged by the RFC and would corrupt the data stream >>>> for fallback sockets. >>>> >>>> Move the conditional reschedule in release_cb() to take action only >>>> after the first loop iteration, to avoid rescheduling just before >>>> releasing the lock. >>>> >>>> Special care is needed to avoid adding skbs to the backlog of a closed >>>> msk and to avoid leaving dangling references into the backlog >>>> at subflow closing time. >> >> (...) >> >>>> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c >>>> index 5a1d8f9e0fb0ec..0aae17ab77edb2 100644 >>>> --- a/net/mptcp/protocol.c >>>> +++ b/net/mptcp/protocol.c >> >> (...) >> >>>> -static bool __mptcp_move_skbs(struct sock *sk) >>>> +static bool mptcp_can_spool_backlog(struct sock *sk, u32 moved, >>>> +                    struct list_head *skbs) >>>>  { >>>> -    struct mptcp_subflow_context *subflow; >>>>      struct mptcp_sock *msk = mptcp_sk(sk); >>>> -    bool ret = false; >>>> >>>> -    if (list_empty(&msk->conn_list)) >>>> +    if (list_empty(&msk->backlog_list)) >>>>          return false; >>>> >>>> -    subflow = list_first_entry(&msk->conn_list, >>>> -                   struct mptcp_subflow_context, node); >>>> -    for (;;) { >>>> -        struct sock *ssk; >>>> -        bool slowpath; >>>> +    /* Borrowed mem could be zero only in the unlikely event that >>>> the bl >>>> +     * is full >>>> +     */ >>>> +    if (likely(msk->borrowed_mem)) { >>>> +        sk_forward_alloc_add(sk, msk->borrowed_mem); >>>> +        msk->borrowed_mem = 0; >>>> +        sk->sk_reserved_mem = msk->backlog_len; >>> >>> With the above I intended to prevent the fwd memory handling from >>> releasing backlog_len bytes. Re-reading the relevant code, it does not >>> allow that (experimentation confirmed), see: >>> >>> https://elixir.bootlin.com/linux/v6.18-rc2/source/include/net/ >>> sock.h#L1593 >>> >>> and: >>> >>> https://elixir.bootlin.com/linux/v6.18-rc2/source/include/net/ >>> sock.h#L1580 >>> >>> This will need some more care. Also patch 2 will require some >>> significant rework. >> >> Thank you for looking at this complex part, and for having spot that! >> >>> @Mat, @Matttbe: could you please consider merging patches 1,3-9? >>> >>> I think they should be pretty uncontroversial, would make the series >>> more manegeable for future iterations (and would alleviate my >>> frustration to make this thing work correctly). >> >> It makes sense, fine by me. I will wait for Mat's review before applying >> them (patch 1 is for 'net' I suppose). >> > > Applying 1,3-9 to our tree(s) makes sense to me. Maybe patch 5 to -net > too? (just sent email about that before I saw this message). Good catch! (I will wait for Paolo's reply before applying the patches.) > Matthieu do you want me to reply to each so the RvB tag is in patchwork, > or does this suffice for patches 1 & 3-9: > > Reviewed-by: Mat Martineau No, that's fine, I can do a copy-paste. (Note that you can also send it as a reply to the cover-letter, then I simply only apply the mentioned patches.) Cheers, Matt -- Sponsored by the NGI0 Core fund.