From nobody Tue Sep 22 08:37:51 2026 Received: from sender4-of-o52.zoho.com (sender4-of-o52.zoho.com [136.143.188.52]) (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 9D92F3451A6 for ; Sun, 26 Jul 2026 05:56:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.52 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785045366; cv=pass; b=kcRsFaogyd9yj93zqKQWTB2xW++qv9tGQdG95PxZwq7/JA+r1jG7+J9f0bpROHPvMXKX1GLqJnsztTjDAV/ymTIpjVR0OGHpd/F5PTiorrKl6qSybckMHMVlPCLWSWZ76HuW1ByTOhIucsF1lE3EOCXBt7y/avK1c4VKDW5fqVE= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785045366; c=relaxed/simple; bh=Wcl1OWRiaFLVILmKZz6aZn8uCA7GjZEbPMOJ+sshIak=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=DN8g3BBZC8yBkZvOkYMHmbS2hYtof+04x9T1vnb3tTvE3nOFptEVacrTKPN1Rs81QCEiFE+DpEzFUzwWPx3VP5dG9eqy0FfvcxHuTp0WDKF2HouwqBS9UqN1FcDvMmqw3jApCbTSt4ZJZX1tJEk4i+mKVaafKM/8Y2wyLvsNhRo= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mpiricsoftware.com; spf=pass smtp.mailfrom=mpiricsoftware.com; dkim=fail (0-bit key) header.d=mpiricsoftware.com header.i=shardul.b@mpiricsoftware.com header.b=jbi1Hhvc reason="key not found in DNS"; arc=pass smtp.client-ip=136.143.188.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mpiricsoftware.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mpiricsoftware.com Authentication-Results: smtp.subspace.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=mpiricsoftware.com header.i=shardul.b@mpiricsoftware.com header.b="jbi1Hhvc" ARC-Seal: i=1; a=rsa-sha256; t=1785045353; cv=none; d=zohomail.com; s=zohoarc; b=KnHbiCLnkordcWjHpJXxEYdTCRYaKdF5KpN6UEFvqknEPyJiAyCYHPXSim4+S4abNQ+U66qjUHnUez83wVdKAtLW+eZ2d/qiZSaeMH/qphKcsCTFlVCTlm5e9nvLpEVPO4Jc+aB/xUqyNJjYO2W8UK/82hFjP29IFJR5D2OL4Sk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1785045353; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:Subject:Subject:To:To:Message-Id:Reply-To; bh=Tqt2yBJEanyGRFea0nNwPoftyscrGxxlGP6g7vyJOzI=; b=BxFNY/kvZI7Mgv20lYKetKHzcXPJkP7XmqTyDONMJZt9pg2Nf9iuoyQrXbD1AUZzC11so6d9Fq4mcynH9k3+qXWTHe744fLhL4HzaSG41nRgxIYsJoyhjbbH4qrf287xhQSrPALtisVpH5WYUwD5paLcqZKq1S3urnbOiapOvbs= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=mpiricsoftware.com; spf=pass smtp.mailfrom=shardul.b@mpiricsoftware.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1785045353; s=mpiric; d=mpiricsoftware.com; i=shardul.b@mpiricsoftware.com; h=From:From:Date:Date:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Message-Id:In-Reply-To:To:To:Cc:Cc:Reply-To; bh=Tqt2yBJEanyGRFea0nNwPoftyscrGxxlGP6g7vyJOzI=; b=jbi1Hhvc24bV7oQI/UWcBtav4ZkB54kWMi9oGX0ak3SOOqkKyH5d9vODckcPmZkX QqWufQdwOTiOYm3C7GP0J5RCyt9SHRmnKAAgb1+lxxwW2Nyy//yVP9WYMOdmq/wroS7 NUj9Zoepr9QYLePQRjE2r/zET12qIU7RKa6q0g78= Received: by mx.zohomail.com with SMTPS id 1785045351427869.0745547738172; Sat, 25 Jul 2026 22:55:51 -0700 (PDT) From: Shardul Bankar Date: Sun, 26 Jul 2026 11:25:41 +0530 Subject: [PATCH mptcp-next 3/3] DO-NOT-MERGE: mptcp: sched: penalise counters Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260726-mptcp_penalise_send-v1-3-84485e0e995b@mpiricsoftware.com> References: <20260726-mptcp_penalise_send-v1-0-84485e0e995b@mpiricsoftware.com> In-Reply-To: <20260726-mptcp_penalise_send-v1-0-84485e0e995b@mpiricsoftware.com> To: "Matthieu Baerts (NGI0)" , MPTCP Linux Cc: shardulsb08@gmail.com, Shardul Bankar X-Mailer: b4 0.15.2 X-ZohoMailClient: External Instrumentation for validating the two preceding patches; not for merge. Adds two MPTcpExt SNMP counters: - CwndPenalized: times a subflow cwnd was actually halved; - PenalCandidate: times the rate trigger picked a slow subflow. Together they separate "the guard held the penalty back" (PenalCandidate high, CwndPenalized ~0) from "the trigger never fired" (both ~0), which is what the receive-window-limited case needs to be read correctly. Co-developed-by: Matthieu Baerts (NGI0) Signed-off-by: Shardul Bankar --- net/mptcp/mib.c | 2 ++ net/mptcp/mib.h | 2 ++ net/mptcp/protocol.c | 8 ++++++++ 3 files changed, 12 insertions(+) diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c index d9bd4f4afcc0..1299613e183b 100644 --- a/net/mptcp/mib.c +++ b/net/mptcp/mib.c @@ -88,6 +88,8 @@ static const struct snmp_mib mptcp_snmp_list[] =3D { SNMP_MIB_ITEM("BacklogDrop", MPTCP_MIB_BACKLOGDROP), SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED), SNMP_MIB_ITEM("OfoPruned", MPTCP_MIB_OFO_PRUNED), + SNMP_MIB_ITEM("CwndPenalized", MPTCP_MIB_CWNDPENALIZED), + SNMP_MIB_ITEM("PenalCandidate", MPTCP_MIB_PENALCAND), }; =20 /* mptcp_mib_alloc - allocate percpu mib counters diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h index 18f35f7e0a2d..93b3a7e9584f 100644 --- a/net/mptcp/mib.h +++ b/net/mptcp/mib.h @@ -91,6 +91,8 @@ enum linux_mptcp_mib_field { MPTCP_MIB_BACKLOGDROP, /* Backlog over memory limit */ MPTCP_MIB_RCVPRUNED, /* Dropped due to memory constrains */ MPTCP_MIB_OFO_PRUNED, /* MPTCP-level OoO queue pruned */ + MPTCP_MIB_CWNDPENALIZED, /* DEBUG: subflow cwnd halved by the scheduler (= #345) */ + MPTCP_MIB_PENALCAND, /* DEBUG: picker chose a slow (low-rate) subflow */ __MPTCP_MIB_MAX }; =20 diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 7cbc5aa17e22..80866f09831a 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1607,6 +1607,7 @@ static void mptcp_penalise_cwnd(struct sock *ssk) subflow->penalise =3D false; subflow->last_penalise =3D tcp_jiffies32; tcp_snd_cwnd_set(tp, max_t(u32, cwnd >> 1, 2)); + MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_CWNDPENALIZED); if (cwnd >=3D tp->snd_ssthresh) tp->snd_ssthresh =3D max_t(u32, tp->snd_ssthresh >> 1, 2); } @@ -1694,6 +1695,13 @@ struct sock *mptcp_subflow_get_send(struct mptcp_soc= k *msk) * once per RTT. */ subflow =3D mptcp_subflow_ctx(ssk); + /* DEBUG: count how often the trigger picks a slow path, so a gated-off + * run (PenalCandidate high, CwndPenalized 0) is distinguishable from one + * where the trigger never fired. + */ + if (fastest && ssk !=3D fastest && + (u64)subflow->avg_pacing_rate * MPTCP_PENALISE_RATE_RATIO < max_pace) + MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_PENALCAND); subflow->penalise =3D fastest && ssk !=3D fastest && (u64)subflow->avg_pacing_rate * MPTCP_PENALISE_RATE_RATIO < max_pac= e && inet_csk(ssk)->icsk_ca_state =3D=3D TCP_CA_Open && --=20 2.34.1