From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) (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 798CD1BF31 for ; Thu, 30 May 2024 01:08:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.110 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717031324; cv=none; b=d8htbPQCXiM9HkC6NRcwYEHK4wB3HpDsh2HmzAMaQdnFc6EmTyGXL/Vl5PHsR7cqLs3P7tO2uM2LodTThr9f9NZNFM6dajjR2+OAVzejURFvjzz1L1IBSWofQK3pTYRL8k9ulLDH59U+xZAVDcJTcopZ2WQpwNnYn7ic2kmNKiU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717031324; c=relaxed/simple; bh=gB8bEZ610lVZ71qkLuw5KH4taGnGkatOCo0aPaqZfXY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Su6Uw+8UerAaoPyVofuz1edEtvIa4ZKAry6X135/JZyl6Y2dm1RBlH0i6JF64iScOS2dD8XQTlYDQUqV8+yo5QJ4XqBV43MB0GkjgoNaav0IWLD300OBmWN9c8KyyxH7t1Ckl6BwoT5EJE5hlioXz85kAVdvaTTFIrbyqphP5Lk= 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=enXq+bZn; arc=none smtp.client-ip=115.124.30.110 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="enXq+bZn" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1717031317; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; bh=NJlhl3JN8DSamcWsAYlYUUsgJOlGWpH3hXAQCcvri6E=; b=enXq+bZnXo0EuV4ZgB8hlkPalMg5FDA2qbxpw1Q+h9ftQxDeA2fvaYcAZln2Wm4caVMmqi256XkG3pBRIRllV2yEQvtDQzolhuXZYR0IB2TOverDv9sqha0ccHKbczlSqMS1bcczqhuyjAHEM4JNDv0cvsLrDbSC7QDGsmAanuw= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045075189;MF=tonylu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0W7Uw2OM_1717031316; Received: from localhost(mailfrom:tonylu@linux.alibaba.com fp:SMTPD_---0W7Uw2OM_1717031316) by smtp.aliyun-inc.com; Thu, 30 May 2024 09:08:37 +0800 Date: Thu, 30 May 2024 09:08:36 +0800 From: Tony Lu To: Jason Xing Cc: Kevin Yang , David Miller , Eric Dumazet , 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 04:49:39PM +0800, Jason Xing wrote: > On Wed, May 29, 2024 at 3:21 PM Tony Lu wrote: > > > > On Tue, May 28, 2024 at 05:13:18PM +0000, Kevin Yang wrote: > > > Adding a sysctl knob to allow user to specify a default > > > rto_min at socket init time. > > > > > > 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. > > > > For series: > > > > Reviewed-by: Tony Lu > > > > I strongly support those patches. For those who use cgroup v1 and want > > to take effect with simple settings, sysctl is a good way. > > It's not a good reason to use sysctl. > > If you say so, why not introduce many sysctls to replace setsockopt > operations. For example, introducing a new sysctl to disable delayed > ack to improve the speed of transmission in some cases just for ease > of use? No, it's not right, I believe. > Hidden behind the words is that if I am a kernel engineer or SRE helping users troubleshoot latency issues, and I need to tune tcp_rto_min, then my only means of not intruding on the application are eBPF or the sysctl mentioned here. Comparing sysctl and eBPF, I prefer sysctl isolated by net namespace, which can be modified and verified more directly and quickly. eBPF is powerful, but it is not easy to write, debug and manage. > > > > And reducing it is helpful for latency-sensitive applications such as > > Redis, net namespace level sysctl knob is enough. > > Sure, these key parameters play a big role in the TCP stack. > > > > > > > > > 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 > > > > >