From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) (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 423B146B6 for ; Fri, 22 Apr 2022 00:04:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650585842; x=1682121842; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=jlBr5zYyDEesZhjSWGHpayndIzP0Qlsf28JHXCiaGww=; b=DPdbBRJ49ro3s2ULwuDZL58HM7UqCtVom1ruqUU+B432UNUM2WayJqrS Ru0dSBe4+DGNaOh6W2HdaaiWDl+h1z+fftCbElNLxSwL1TWNLlOoxPb31 hySG9/la4lBc8gGwvOQ+USeVXiFsYcGSAx5zEp78NekSRcn41Vkl33apW 00l0KuD+GK9uwV0SU/hl29VK5vgieEfE/RkLYsqj8pXKwS1inDBEqS5Se aTmmQkWquw4XJ7kfuZ2VV5YxG03bxqNquq5UfEBHvYvVIsZwmherC1MpE OWiHEk5zB8/KpiI/nhFKH8iLTiLTZr8a1eKirbsp1jBU4SWLmVF/aJStt Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10324"; a="264293022" X-IronPort-AV: E=Sophos;i="5.90,280,1643702400"; d="scan'208";a="264293022" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2022 17:04:01 -0700 X-IronPort-AV: E=Sophos;i="5.90,280,1643702400"; d="scan'208";a="658753912" Received: from dolaleye-mobl.amr.corp.intel.com ([10.209.117.155]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2022 17:04:01 -0700 Date: Thu, 21 Apr 2022 17:04:00 -0700 (PDT) From: Mat Martineau To: Paolo Abeni cc: mptcp@lists.linux.dev Subject: Re: [PATCH v2 0/5] mptcp: improve mptcp-level window tracking In-Reply-To: Message-ID: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed On Thu, 21 Apr 2022, Paolo Abeni wrote: > I've been chasing bad/unstable performances with multiple subflows > on very high speed links. > > It looks like the root cause is due to the current mptcp-level > congestion window handling. There are apparently a few different > sub-issues: > > - the rcv_wnd is not effectively shared on the tx side, as each > subflow takes in account only the value received by the underlaying > TCP connection. This is addressed in patch 1/4 > > - The mptcp-level offered wnd right edge is currently allowed to shrink. > Reading section 3.3.4.: > > """ > The receive window is relative to the DATA_ACK. As in TCP, a > receiver MUST NOT shrink the right edge of the receive window (i.e., > DATA_ACK + receive window). The receiver will use the data sequence > number to tell if a packet should be accepted at the connection > level. > """ > > I read the above as we need to reflect window right-edge tracking > on the wire, see patch 3/4. > > - The offered window right edge tracking can happen concurrently on > multiple subflows, but there is no mutex protection. We need an > additional atomic operation - still patch 3/4 > > This series additionally bump a few new MIBs to track all the above > (ensure/observe that the suspected races actually take place). > > I could not access again the host where the issue was su much > noticeable, still in the current setup the tput changes from > [6-18] Gbps to 19Gbps very stable. > > v1 -> v2: > - pass only the TCP header to tcp_options_write (Mat) > - fix build issues on some 32 bit arches (intel bot) v2 looks good for the export branch, thanks Paolo. Reviewed-by: Mat Martineau > > RFC -> v1: > - added patch 3/5 to address Mat's comment, and rebased the > following on top of it - I hope Eric may tolerate that, it's > more an hope than guess ;) > > Paolo Abeni (5): > mptcp: really share subflow snd_wnd > mptcp: add mib for xmit window sharing > tcp: allow MPTCP to update the announced window. > mptcp: never shrink offered window > mptcp: add more offered MIBs counter. > > include/net/mptcp.h | 2 +- > net/ipv4/tcp_output.c | 14 ++++++----- > net/mptcp/mib.c | 4 +++ > net/mptcp/mib.h | 6 +++++ > net/mptcp/options.c | 58 +++++++++++++++++++++++++++++++++++++------ > net/mptcp/protocol.c | 32 +++++++++++++++--------- > net/mptcp/protocol.h | 2 +- > 7 files changed, 90 insertions(+), 28 deletions(-) > > -- > 2.35.1 > > > -- Mat Martineau Intel