From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-111.freemail.mail.aliyun.com (out30-111.freemail.mail.aliyun.com [115.124.30.111]) (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 3AA11167D80 for ; Wed, 29 May 2024 07:56:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.111 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716969382; cv=none; b=EgLl/7DyugYj9V27e3gLHxppREMxL7O7MoHPUMBZ4oc4W7GU25vbusz5lUFYY9ArRlRR4ZTiGdVyi0Vx/OW5lICtVHpIXend9Gu+0FgHM6wLPT8QwKsGxrrwWq0GTcm1IDYcxBJthZRrexxpS9Rw9O8SJjg04PaPVKr7eofU1Zk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716969382; c=relaxed/simple; bh=3tIN3IW27wnKXrnEiPiaPMCMWqpvfID4cd7qOMCqn/s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mdUBEbUDN+rOsBtIsk1c2vBmoFCXClTA62wtDEVWcNuD4+pY3dPddUyBL6P5yXPPKpNFH2b4xJ0bYHT6B1KpWazzaEsiUKGxog4frh+Z9+RCxp0RJ8+ubcLDNWr8t0nczsR7uZHmAq87CTzkwf4chG7IKwzlYyaUntKFsmUouJE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=h2dap/eV; arc=none smtp.client-ip=115.124.30.111 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="h2dap/eV" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1716969371; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; bh=2PYb9pB+7U+P7EtpBENK4iIFVLPhWz3/O4ZdjUNs/vg=; b=h2dap/eVXTJ8O4IUfEM6bPYxr9IMmffOl1hG7zbbhNjcH8Ogv6nB+KvDTcY1PRZeFIYV+BCTmbC09RvbLMfk0c++OkBiWftytWJe7dsdZP0ETF3/2S/9ZrebgvbNEkuKJHJ30I2CVNFtKR4YUmdSmDHCwokcuiwkwnca7+VE6kw= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R241e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037067110;MF=tonylu@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0W7S3tLI_1716969370; Received: from localhost(mailfrom:tonylu@linux.alibaba.com fp:SMTPD_---0W7S3tLI_1716969370) by smtp.aliyun-inc.com; Wed, 29 May 2024 15:56:10 +0800 Date: Wed, 29 May 2024 15:56:08 +0800 From: Tony Lu To: Eric Dumazet Cc: Jason Xing , Kevin Yang , Paolo Abeni , David Miller , Jakub Kicinski , netdev@vger.kernel.org Subject: Re: [PATCH net-next 0/2] tcp: add sysctl_tcp_rto_min_us Message-ID: Reply-To: Tony Lu References: <20240528171320.1332292-1-yyd@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, May 29, 2024 at 09:39:02AM +0200, Eric Dumazet wrote: > On Wed, May 29, 2024 at 9:00 AM Jason Xing wrote: > > > > On Wed, May 29, 2024 at 2:43 PM Jason Xing wrote: > > > > > > Hello Kevin, > > > > > > On Wed, May 29, 2024 at 1:13 AM Kevin Yang wrote: > > > > > > > > Adding a sysctl knob to allow user to specify a default > > > > rto_min at socket init time. > > > > > > I wonder what the advantage of this new sysctl knob is since we have > > > had BPF or something like that to tweak the rto min already? > > > > > > There are so many places/parameters of the TCP stack that can be > > > exposed to the user side and adjusted by new sysctls... > > > > > > Thanks, > > > Jason > > > > > > > > > > > After this patch series, the rto_min will has multiple sources: > > > > route option has the highest precedence, followed by the > > > > TCP_BPF_RTO_MIN socket option, followed by this new > > > > tcp_rto_min_us sysctl. > > > > > > > > Kevin Yang (2): > > > > tcp: derive delack_max with tcp_rto_min helper > > > > tcp: add sysctl_tcp_rto_min_us > > > > > > > > Documentation/networking/ip-sysctl.rst | 13 +++++++++++++ > > > > include/net/netns/ipv4.h | 1 + > > > > net/ipv4/sysctl_net_ipv4.c | 8 ++++++++ > > > > net/ipv4/tcp.c | 3 ++- > > > > net/ipv4/tcp_ipv4.c | 1 + > > > > net/ipv4/tcp_output.c | 11 ++--------- > > > > 6 files changed, 27 insertions(+), 10 deletions(-) > > > > > > > > -- > > > > 2.45.1.288.g0e0cd299f1-goog > > > > > > > > > > > > Oh, I think you should have added Paolo as well. > > > > +Paolo Abeni > > Many cloud customers do not have any BPF expertise. > If they use existing BPF programs (added by a product), they might not > have the ability to change it. +1, eBPF actually is not easy to write, debug and manage for now. Sysctls are easy to use, just put it into /etc/sysctl.conf and save it into users' customized images or templates. AFAIK, there is no standard system kit to handle eBPF in most OS distros. > > We tried advising them to use route attributes, after > commit bbf80d713fe75cfbecda26e7c03a9a8d22af2f4f ("tcp: derive > delack_max from rto_min") > > Alas, dhcpd was adding its own routes, without the "rto_min 5" > attribute, then systemd came... > Lots of frustration, lots of wasted time, for something that has been > used for more than a decade > in Google DC. > > With a sysctl, we could have saved months of SWE, and helped our > customers sooner. > > Reviewed-by: Eric Dumazet