From nobody Thu Nov 27 12:35:28 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 D48F6372AA5 for ; Wed, 19 Nov 2025 21:54:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763589277; cv=none; b=QFomk0mKw9e5XcY47CN45FZ672Vt9bIo4O/fsADz8gpJ+W4WAWq2jyQl4Upw/HncZW9r6BQqrKdisKaWTwSP+dtzFzGESEtI7rpEsDy0A3WO/ftPblq2dvqHd1Tsb9ew+xFh4FN3P+liV3oOJaoIEnKKn9E/HW6loCPCdeGWxq4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763589277; c=relaxed/simple; bh=aURQQXEryRFfJjkaU6HdjVlmD3kMg+HHLP7Rbjx7jeg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=OpKyjPOKH+fIo9Gu4zI2GKmUE3xV1fsdG411WM/GDdqzjcVp0xaMqyk/yQSOgElv+QT2R6CG/Ohs94hA+Df4FRGdPsVHBTjTKRLgYL0fPpNMccNWtf7lD+H9aftuVfmftFnvcdmV2g5BKaW2a82+u29uFLnT4N94Jzlwqn17UUI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=dmBD0x6U; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="dmBD0x6U" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763589274; 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=sVyLFxsoy29T4gggCzNi54Gin1PHAW9O695ZnK7TPeY=; b=dmBD0x6UAice1BG+WEpfFMJMM+lEX51z2YJ/ws+mIWu3w+lWsXJO4HFb8VNVrHXEFUvL/W k91VaS4hQwCYVbLcOFTms/7tmS5P3QKypqh2RN2OCVFyJfvyY4GQVmNZRIIKdPFVasMPoZ +k+PFMeu9cVJdjnf5u84HnV7v1753AM= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-442-cBFf3jYQNO6f4NtPJNA1Gg-1; Wed, 19 Nov 2025 16:54:32 -0500 X-MC-Unique: cBFf3jYQNO6f4NtPJNA1Gg-1 X-Mimecast-MFC-AGG-ID: cBFf3jYQNO6f4NtPJNA1Gg_1763589271 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 875A6195608E; Wed, 19 Nov 2025 21:54:31 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.33.89]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 71DB118004A3; Wed, 19 Nov 2025 21:54:30 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Cc: martineau@kernel.org Subject: [PATCH mptcp-next v6 1/4] trace: mptcp: add mptcp_rcvbuf_grow tracepoint Date: Wed, 19 Nov 2025 22:54:20 +0100 Message-ID: <80017719d0443742e0d5a26de64da5570a85fc54.1763588352.git.pabeni@redhat.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 93JvExES3R6xOmVrwxGGy7UEkcWT-Oy15HLStfzcpxY_1763589271 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" Similar to tcp, provide a new tracepoint to better understand mptcp_rcv_space_adjust() behavior, which presents many artifacts. Note that the used format string is so long that I preferred wrap it, contrary to guidance for quoted strings. Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni --- v4 -> v5: - fixed a couple of checkpatch issues. v2 -> v3: - use __entry->family; note that its value is show as raw number instead of string, as show_family_name is available only to net/core/ trace and I preferred not moving the mptcp traces there as we need mptcp-specific helpers, too. --- include/trace/events/mptcp.h | 80 ++++++++++++++++++++++++++++++++++++ net/mptcp/protocol.c | 3 ++ 2 files changed, 83 insertions(+) diff --git a/include/trace/events/mptcp.h b/include/trace/events/mptcp.h index 085b749cdd97..269d949b2025 100644 --- a/include/trace/events/mptcp.h +++ b/include/trace/events/mptcp.h @@ -5,7 +5,13 @@ #if !defined(_TRACE_MPTCP_H) || defined(TRACE_HEADER_MULTI_READ) #define _TRACE_MPTCP_H =20 +#include +#include #include +#include +#include +#include +#include =20 #define show_mapping_status(status) \ __print_symbolic(status, \ @@ -178,6 +184,80 @@ TRACE_EVENT(subflow_check_data_avail, __entry->skb) ); =20 +#include + +TRACE_EVENT(mptcp_rcvbuf_grow, + + TP_PROTO(struct sock *sk, int time), + + TP_ARGS(sk, time), + + TP_STRUCT__entry( + __field(int, time) + __field(__u32, rtt_us) + __field(__u32, copied) + __field(__u32, inq) + __field(__u32, space) + __field(__u32, ooo_space) + __field(__u32, rcvbuf) + __field(__u32, rcv_wnd) + __field(__u8, scaling_ratio) + __field(__u16, sport) + __field(__u16, dport) + __field(__u16, family) + __array(__u8, saddr, 4) + __array(__u8, daddr, 4) + __array(__u8, saddr_v6, 16) + __array(__u8, daddr_v6, 16) + __field(const void *, skaddr) + ), + + TP_fast_assign( + struct mptcp_sock *msk =3D mptcp_sk(sk); + struct inet_sock *inet =3D inet_sk(sk); + bool ofo_empty; + __be32 *p32; + + __entry->time =3D time; + __entry->rtt_us =3D msk->rcvq_space.rtt_us >> 3; + __entry->copied =3D msk->rcvq_space.copied; + __entry->inq =3D mptcp_inq_hint(sk); + __entry->space =3D msk->rcvq_space.space; + ofo_empty =3D RB_EMPTY_ROOT(&msk->out_of_order_queue); + __entry->ooo_space =3D ofo_empty ? 0 : + MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq - + msk->ack_seq; + + __entry->rcvbuf =3D sk->sk_rcvbuf; + __entry->rcv_wnd =3D atomic64_read(&msk->rcv_wnd_sent) - + msk->ack_seq; + __entry->scaling_ratio =3D msk->scaling_ratio; + __entry->sport =3D ntohs(inet->inet_sport); + __entry->dport =3D ntohs(inet->inet_dport); + __entry->family =3D sk->sk_family; + + p32 =3D (__be32 *)__entry->saddr; + *p32 =3D inet->inet_saddr; + + p32 =3D (__be32 *)__entry->daddr; + *p32 =3D inet->inet_daddr; + + TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr, + sk->sk_v6_rcv_saddr, sk->sk_v6_daddr); + + __entry->skaddr =3D sk; + ), + + TP_printk("time=3D%u rtt_us=3D%u copied=3D%u inq=3D%u space=3D%u ooo=3D%u= scaling_ratio=3D%u " + "rcvbuf=3D%u rcv_wnd=3D%u family=3D%d sport=3D%hu dport=3D%hu saddr=3D= %pI4 " + "daddr=3D%pI4 saddrv6=3D%pI6c daddrv6=3D%pI6c skaddr=3D%p", + __entry->time, __entry->rtt_us, __entry->copied, + __entry->inq, __entry->space, __entry->ooo_space, + __entry->scaling_ratio, __entry->rcvbuf, __entry->rcv_wnd, + __entry->family, __entry->sport, __entry->dport, + __entry->saddr, __entry->daddr, __entry->saddr_v6, + __entry->daddr_v6, __entry->skaddr) +); #endif /* _TRACE_MPTCP_H */ =20 /* This part must be outside protection */ diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index f8756521b2e2..64f592a7897c 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -28,6 +28,8 @@ #include "protocol.h" #include "mib.h" =20 +static unsigned int mptcp_inq_hint(const struct sock *sk); + #define CREATE_TRACE_POINTS #include =20 @@ -2118,6 +2120,7 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock = *msk, int copied) if (msk->rcvq_space.copied <=3D msk->rcvq_space.space) goto new_measure; =20 + trace_mptcp_rcvbuf_grow(sk, time); if (mptcp_rcvbuf_grow(sk, msk->rcvq_space.copied)) { /* Make subflows follow along. If we do not do this, we * get drops at subflow level if skbs can't be moved to --=20 2.51.1 From nobody Thu Nov 27 12:35:28 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 3D9D33002D6 for ; Wed, 19 Nov 2025 21:54:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763589277; cv=none; b=G8vUVTjua5gFFJq2RbMZnuGhn8Q+7i977lbJiW4aA64mDhuYoj4aaWpCwbUPLjZ/ol5bl6WjiHAfw2YVJWlsv86Mfe42DVwuu/+00T/RJoY7/AxdCENHq555dM0q3LBK/58RQ8y/VM6y7skGCWHmgDFoBariSxEHVsy5gLdKrk0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763589277; c=relaxed/simple; bh=PdayE6EmgxNaInJNbKO98vucGv/vB+l2r4wmbQmD+Mk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=KrubrgfhR9hQ4M+SPj7BFJ5hrlOx2jMPTvUPjN9m0DtScBtCJoQ1wsAnACyLaQPAelBwKvpaDacJVlmhpZDTxATz7XdFcYKaK9TYsKYkKtjBUgmYdzpS59pYbkxSfqgMsdslmWMjLAD3Vw+H5f3tlWO9v2ldOf45JpHyfzfVJ3c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=gbDeZqG+; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gbDeZqG+" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763589275; 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=2jzQmXOwwYh0MDj+JEbfYJZDZFWE8zZpArcIShBQbyI=; b=gbDeZqG+nirECSjGu7SWhtYvZp9ARety0NL5Y9gplhqpBx0fBt8MTD6cPQ9m1JBNLL34eG SeX2K0TNeRvZA07kPV/G8HIUaI9/GDHOFUjKJmpLdvGV+rQoZ+wnQqOh1qYNItmDzoxUHK kg9jxW2L1UEpyL2NaC40z9OUlpgakQU= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-639-wp7v8sYpPGCegc4w_vpYxA-1; Wed, 19 Nov 2025 16:54:34 -0500 X-MC-Unique: wp7v8sYpPGCegc4w_vpYxA-1 X-Mimecast-MFC-AGG-ID: wp7v8sYpPGCegc4w_vpYxA_1763589273 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4DCE3180034F; Wed, 19 Nov 2025 21:54:33 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.33.89]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 2E7EE180049F; Wed, 19 Nov 2025 21:54:31 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Cc: martineau@kernel.org Subject: [PATCH mptcp-next v6 2/4] mptcp: fix receive space timestamp initialization. Date: Wed, 19 Nov 2025 22:54:21 +0100 Message-ID: <811d8cc6f0b9bfa6080bd108805cabc021b3e9a5.1763588352.git.pabeni@redhat.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: WbSNSLOgIhfLbUD7Qor5h9NTr_D9kS9TWT5uC6K5lc4_1763589273 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" MPTCP initialize the receive buffer stamp in mptcp_rcv_space_init(), using the provided subflow stamp. Such helper is invoked in several places; for passive sockets, space init happened at clone time. In such scenario, MPTCP ends-up accesses the subflow stamp before its initialization, leading to quite randomic timing for the first receive buffer auto-tune event, as the timestamp for newly created subflow is not refreshed there. Fix the issue moving the stamp initialization out of the mentioned helper, at the data transfer start, and always using a fresh timestamp. Fixes: 013e3179dbd2 ("mptcp: fix rcv space initialization") Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni --- v5 -> v6 - really remove the stamp init from mptcp_rcv_space_init() v1 -> v2: - factor out only the tstamp change for better reviewability --- net/mptcp/protocol.c | 9 ++++----- net/mptcp/protocol.h | 5 +++++ 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 64f592a7897c..d6d2d9d1849a 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2089,8 +2089,8 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock = *msk, int copied) =20 msk->rcvq_space.copied +=3D copied; =20 - mstamp =3D div_u64(tcp_clock_ns(), NSEC_PER_USEC); - time =3D tcp_stamp_us_delta(mstamp, msk->rcvq_space.time); + mstamp =3D mptcp_stamp(); + time =3D tcp_stamp_us_delta(mstamp, READ_ONCE(msk->rcvq_space.time)); =20 rtt_us =3D msk->rcvq_space.rtt_us; if (rtt_us && time < (rtt_us >> 3)) @@ -3530,7 +3530,7 @@ struct sock *mptcp_sk_clone_init(const struct sock *s= k, mptcp_copy_inaddrs(nsk, ssk); __mptcp_propagate_sndbuf(nsk, ssk); =20 - mptcp_rcv_space_init(msk, ssk); + msk->rcvq_space.time =3D mptcp_stamp(); =20 if (mp_opt->suboptions & OPTION_MPTCP_MPC_ACK) __mptcp_subflow_fully_established(msk, subflow, mp_opt); @@ -3548,8 +3548,6 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, con= st struct sock *ssk) msk->rcvq_space.copied =3D 0; msk->rcvq_space.rtt_us =3D 0; =20 - msk->rcvq_space.time =3D tp->tcp_mstamp; - /* initial rcv_space offering made to peer */ msk->rcvq_space.space =3D min_t(u32, tp->rcv_wnd, TCP_INIT_CWND * tp->advmss); @@ -3745,6 +3743,7 @@ void mptcp_finish_connect(struct sock *ssk) * accessing the field below */ WRITE_ONCE(msk->local_key, subflow->local_key); + WRITE_ONCE(msk->rcvq_space.time, mptcp_stamp()); =20 mptcp_pm_new_connection(msk, ssk, 0); } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 199f28f3dd5e..95c62f2ac705 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -917,6 +917,11 @@ static inline bool mptcp_is_fully_established(struct s= ock *sk) READ_ONCE(mptcp_sk(sk)->fully_established); 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Wed, 19 Nov 2025 21:54:35 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.33.89]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 2CA6C180049F; Wed, 19 Nov 2025 21:54:33 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Cc: martineau@kernel.org Subject: [PATCH mptcp-next v6 3/4] mptcp: better mptcp-level RTT estimator Date: Wed, 19 Nov 2025 22:54:22 +0100 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: CNYOd0zqE3w-jsIinE3DKwmmEryVZW3fx05Ghd6VGlw_1763589275 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" The current MPTCP-level RTT estimator has several issues. On high speed links, the MPTCP-level receive buffer auto-tuning happens with a frequency well above the TCP-level's one. That in turn can cause excessive/unneeded receive buffer increase. On such links, the initial rtt_us value is considerably higher than the actual delay, and the current mptcp_rcv_space_adjust() updates msk->rcvq_space.rtt_us with a period equal to the such field previous value. If the initial rtt_us is 40ms, its first update will happen after 40ms, even if the subflows see actual RTT orders of magnitude lower. Additionally: - setting the msk rtt to the maximum among all the subflows RTTs makes DRS constantly overshooting the rcvbuf size when a subflow has considerable higher latency than the other(s). - during unidirectional bulk transfers with multiple active subflows, the TCP-level RTT estimator occasionally sees considerably higher value than the real link delay, i.e. when the packet scheduler reacts to an incoming ack on given subflow pushing data on a different subflow. - currently inactive but still open subflows (i.e. switched to backup mode) are always considered when computing the msk-level rtt. Address the all the issues above with a more accurate RTT estimation strategy: the MPTCP-level RTT is set to the minimum of all the subflows actually feeding data into the MPTCP receive buffer, using a small sliding window. While at it, also use EWMA to compute the msk-level scaling_ratio, to that mptcp can avoid traversing the subflow list is mptcp_rcv_space_adjust(). Use some care to avoid updating msk and ssk level fields too often. Fixes: a6b118febbab ("mptcp: add receive buffer auto-tuning") Signed-off-by: Paolo Abeni --- v4 -> v5: - avoid filtering out too high value, use sliding window instead v3 -> v4: - really refresh msk rtt after a full win per subflow (off-by-one in prev revision) - sync mptcp_rcv_space_adjust() comment with the new code v1 -> v2: - do not use explicit reset flags - do rcv win based decision instead - discard 0 rtt_us samples from subflows - discard samples on non empty rx queue - discard "too high" samples, see the code comments WRT the whys --- include/trace/events/mptcp.h | 2 +- net/mptcp/protocol.c | 63 ++++++++++++++++++++---------------- net/mptcp/protocol.h | 38 +++++++++++++++++++++- 3 files changed, 73 insertions(+), 30 deletions(-) diff --git a/include/trace/events/mptcp.h b/include/trace/events/mptcp.h index 269d949b2025..04521acba483 100644 --- a/include/trace/events/mptcp.h +++ b/include/trace/events/mptcp.h @@ -219,7 +219,7 @@ TRACE_EVENT(mptcp_rcvbuf_grow, __be32 *p32; =20 __entry->time =3D time; - __entry->rtt_us =3D msk->rcvq_space.rtt_us >> 3; + __entry->rtt_us =3D mptcp_rtt_us_est(msk) >> 3; __entry->copied =3D msk->rcvq_space.copied; __entry->inq =3D mptcp_inq_hint(sk); __entry->space =3D msk->rcvq_space.space; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index d6d2d9d1849a..7af4c13b8f60 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -886,6 +886,32 @@ static bool move_skbs_to_msk(struct mptcp_sock *msk, s= truct sock *ssk) return moved; } =20 +static void mptcp_rcv_rtt_update(struct mptcp_sock *msk, + struct mptcp_subflow_context *subflow) +{ + const struct tcp_sock *tp =3D tcp_sk(subflow->tcp_sock); + u32 rtt_us =3D tp->rcv_rtt_est.rtt_us; + int id; + + /* Update once per subflow per rcvwnd to avoid touching the msk + * too often. + */ + if (!rtt_us || tp->rcv_rtt_est.seq =3D=3D subflow->prev_rtt_seq) + return; + + subflow->prev_rtt_seq =3D tp->rcv_rtt_est.seq; + + /* Pairs with READ_ONCE() in mptcp_rtt_us_est(). */ + id =3D msk->rcv_rtt_est.next_sample; + WRITE_ONCE(msk->rcv_rtt_est.samples[id], rtt_us); + if (++msk->rcv_rtt_est.next_sample =3D=3D MPTCP_RTT_SAMPLES) + msk->rcv_rtt_est.next_sample =3D 0; + + /* EWMA among the incoming subflows */ + msk->scaling_ratio =3D ((msk->scaling_ratio << 3) - msk->scaling_ratio + + tp->scaling_ratio) >> 3; +} + void mptcp_data_ready(struct sock *sk, struct sock *ssk) { struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); @@ -899,6 +925,7 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk) return; =20 mptcp_data_lock(sk); + mptcp_rcv_rtt_update(msk, subflow); if (!sock_owned_by_user(sk)) { /* Wake-up the reader only for in-sequence data */ if (move_skbs_to_msk(msk, ssk) && mptcp_epollin_ready(sk)) @@ -2069,15 +2096,15 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, st= ruct msghdr *msg, =20 /* receive buffer autotuning. See tcp_rcv_space_adjust for more informati= on. * - * Only difference: Use highest rtt estimate of the subflows in use. + * Only difference: Use lowest rtt estimate of the subflows in use, see + * mptcp_rcv_rtt_update() and mptcp_rtt_us_est(). */ static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied) { struct mptcp_subflow_context *subflow; struct sock *sk =3D (struct sock *)msk; - u8 scaling_ratio =3D U8_MAX; - u32 time, advmss =3D 1; - u64 rtt_us, mstamp; + u32 time, rtt_us; + u64 mstamp; =20 msk_owned_by_me(msk); =20 @@ -2092,29 +2119,8 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock= *msk, int copied) mstamp =3D mptcp_stamp(); time =3D tcp_stamp_us_delta(mstamp, READ_ONCE(msk->rcvq_space.time)); =20 - rtt_us =3D msk->rcvq_space.rtt_us; - if (rtt_us && time < (rtt_us >> 3)) - return; - - rtt_us =3D 0; - mptcp_for_each_subflow(msk, subflow) { - const struct tcp_sock *tp; - u64 sf_rtt_us; - u32 sf_advmss; - - tp =3D tcp_sk(mptcp_subflow_tcp_sock(subflow)); - - sf_rtt_us =3D READ_ONCE(tp->rcv_rtt_est.rtt_us); - sf_advmss =3D READ_ONCE(tp->advmss); - - rtt_us =3D max(sf_rtt_us, rtt_us); - advmss =3D max(sf_advmss, advmss); - scaling_ratio =3D min(tp->scaling_ratio, scaling_ratio); - } - - msk->rcvq_space.rtt_us =3D rtt_us; - msk->scaling_ratio =3D scaling_ratio; - if (time < (rtt_us >> 3) || rtt_us =3D=3D 0) + rtt_us =3D mptcp_rtt_us_est(msk); + if (rtt_us =3D=3D U32_MAX || time < (rtt_us >> 3)) return; =20 if (msk->rcvq_space.copied <=3D msk->rcvq_space.space) @@ -2960,6 +2966,7 @@ static void __mptcp_init_sock(struct sock *sk) msk->timer_ival =3D TCP_RTO_MIN; msk->scaling_ratio =3D TCP_DEFAULT_SCALING_RATIO; msk->backlog_len =3D 0; + mptcp_init_rtt_est(msk); =20 WRITE_ONCE(msk->first, NULL); inet_csk(sk)->icsk_sync_mss =3D mptcp_sync_mss; @@ -3403,6 +3410,7 @@ static int mptcp_disconnect(struct sock *sk, int flag= s) msk->bytes_sent =3D 0; msk->bytes_retrans =3D 0; msk->rcvspace_init =3D 0; + mptcp_init_rtt_est(msk); =20 /* for fallback's sake */ WRITE_ONCE(msk->ack_seq, 0); @@ -3546,7 +3554,6 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, con= st struct sock *ssk) =20 msk->rcvspace_init =3D 1; msk->rcvq_space.copied =3D 0; - msk->rcvq_space.rtt_us =3D 0; =20 /* initial rcv_space offering made to peer */ msk->rcvq_space.space =3D min_t(u32, tp->rcv_wnd, diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 95c62f2ac705..df33b30043b6 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -269,6 +269,13 @@ struct mptcp_data_frag { struct page *page; }; =20 +/* Arbitrary compromise between as low as possible to react timely to subf= low + * close event and as big as possible to avoid being fouled by biased large + * samples due to peer sending data on a different subflow WRT to the inco= ming + * ack. + */ +#define MPTCP_RTT_SAMPLES 5 + /* MPTCP connection sock */ struct mptcp_sock { /* inet_connection_sock must be the first member */ @@ -340,11 +347,17 @@ struct mptcp_sock { */ struct mptcp_pm_data pm; struct mptcp_sched_ops *sched; + + /* Most recent rtt_us observed by in use incoming subflows. */ + struct { + u32 samples[MPTCP_RTT_SAMPLES]; + u32 next_sample; + } rcv_rtt_est; + struct { int space; /* bytes copied in last measurement window */ int copied; /* bytes copied in this measurement window */ u64 time; /* start time of measurement window */ - u64 rtt_us; /* last maximum rtt of subflows */ } rcvq_space; u8 scaling_ratio; bool allow_subflows; @@ -422,6 +435,27 @@ static inline struct mptcp_data_frag *mptcp_send_head(= const struct sock *sk) return msk->first_pending; } =20 +static inline void mptcp_init_rtt_est(struct mptcp_sock *msk) +{ + int i; + + for (i =3D 0; i < MPTCP_RTT_SAMPLES; ++i) + msk->rcv_rtt_est.samples[i] =3D U32_MAX; + msk->rcv_rtt_est.next_sample =3D 0; + msk->scaling_ratio =3D TCP_DEFAULT_SCALING_RATIO; +} + +static inline u32 mptcp_rtt_us_est(const struct mptcp_sock *msk) +{ + u32 rtt_us =3D msk->rcv_rtt_est.samples[0]; + int i; + + /* Lockless access of collected samples. */ + for (i =3D 1; i < MPTCP_RTT_SAMPLES; ++i) + rtt_us =3D min(rtt_us, READ_ONCE(msk->rcv_rtt_est.samples[i])); + return rtt_us; +} + static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk) { struct mptcp_sock *msk =3D mptcp_sk(sk); 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Wed, 19 Nov 2025 21:54:37 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.33.89]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id EADAD180049F; Wed, 19 Nov 2025 21:54:35 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Cc: martineau@kernel.org Subject: [PATCH mptcp-next v6 4/4] mptcp: add receive queue awareness in tcp_rcv_space_adjust() Date: Wed, 19 Nov 2025 22:54:23 +0100 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: V7bTUoPKbvlLY7qfl6-yT33tLf6SoI2n1tnxvN-oces_1763589277 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" This is the mptcp counter-part of commit ea33537d8292 ("tcp: add receive queue awareness in tcp_rcv_space_adjust()"). Prior to this commit: ESTAB 33165568 0 192.168.255.2:5201 192.168.255.1:53380 \ skmem:(r33076416,rb33554432,t0,tb91136,f448,w0,o0,bl0,d0) After: ESTAB 3279168 0 192.168.255.2:5201 192.168.255.1]:53042 \ skmem:(r3190912,rb3719956,t0,tb91136,f1536,w0,o0,bl0,d0) (same tput) Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni --- net/mptcp/protocol.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 7af4c13b8f60..8d43ad716209 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2123,11 +2123,13 @@ static void mptcp_rcv_space_adjust(struct mptcp_soc= k *msk, int copied) if (rtt_us =3D=3D U32_MAX || time < (rtt_us >> 3)) return; =20 - if (msk->rcvq_space.copied <=3D msk->rcvq_space.space) + copied =3D msk->rcvq_space.copied; + copied -=3D mptcp_inq_hint(sk); + if (copied <=3D msk->rcvq_space.space) goto new_measure; =20 trace_mptcp_rcvbuf_grow(sk, time); - if (mptcp_rcvbuf_grow(sk, msk->rcvq_space.copied)) { + if (mptcp_rcvbuf_grow(sk, copied)) { /* Make subflows follow along. If we do not do this, we * get drops at subflow level if skbs can't be moved to * the mptcp rx queue fast enough (announced rcv_win can @@ -2141,7 +2143,7 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock = *msk, int copied) slow =3D lock_sock_fast(ssk); /* subflows can be added before tcp_init_transfer() */ if (tcp_sk(ssk)->rcvq_space.space) - tcp_rcvbuf_grow(ssk, msk->rcvq_space.copied); + tcp_rcvbuf_grow(ssk, copied); unlock_sock_fast(ssk, slow); } } --=20 2.51.1