From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA170C47257 for ; Tue, 5 May 2020 17:06:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9764206CC for ; Tue, 5 May 2020 17:06:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="bqIIKFLn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730701AbgEERGZ (ORCPT ); Tue, 5 May 2020 13:06:25 -0400 Received: from smtp-fw-33001.amazon.com ([207.171.190.10]:42596 "EHLO smtp-fw-33001.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729553AbgEERGZ (ORCPT ); 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Tue, 5 May 2020 17:06:21 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA002.ant.amazon.com (10.43.61.77) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 5 May 2020 17:06:21 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.180) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 5 May 2020 17:06:11 +0000 From: SeongJae Park To: Eric Dumazet CC: SeongJae Park , Eric Dumazet , David Miller , Al Viro , "Jakub Kicinski" , Greg Kroah-Hartman , , netdev , LKML , SeongJae Park , , , , Paul McKenney Subject: Re: Re: [PATCH net v2 0/2] Revert the 'socket_alloc' life cycle change Date: Tue, 5 May 2020 19:05:53 +0200 Message-ID: <20200505170553.24056-1-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <67bdfac9-0d7d-0bbe-dc7a-d73979fd8ed9@gmail.com> (raw) MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.43.160.180] X-ClientProxiedBy: EX13D10UWB001.ant.amazon.com (10.43.161.111) To EX13D31EUA001.ant.amazon.com (10.43.165.15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 5 May 2020 09:37:42 -0700 Eric Dumazet wrote: > > > On 5/5/20 9:31 AM, Eric Dumazet wrote: > > > > > > On 5/5/20 9:25 AM, Eric Dumazet wrote: > >> > >> > >> On 5/5/20 9:13 AM, SeongJae Park wrote: > >>> On Tue, 5 May 2020 09:00:44 -0700 Eric Dumazet wrote: > >>> > >>>> On Tue, May 5, 2020 at 8:47 AM SeongJae Park wrote: > >>>>> > >>>>> On Tue, 5 May 2020 08:20:50 -0700 Eric Dumazet wrote: > >>>>> > >>>>>> > >>>>>> > >>>>>> On 5/5/20 8:07 AM, SeongJae Park wrote: > >>>>>>> On Tue, 5 May 2020 07:53:39 -0700 Eric Dumazet wrote: > >>>>>>> > >>>>>> [...] > >> > >> I would ask Paul opinion on this issue, because we have many objects > >> being freed after RCU grace periods. > >> > >> If RCU subsystem can not keep-up, I guess other workloads will also suffer. > >> > >> Sure, we can revert patches there and there trying to work around the issue, > >> but for objects allocated from process context, we should not have these problems. > >> > > > > I wonder if simply adjusting rcu_divisor to 6 or 5 would help > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index d9a49cd6065a20936edbda1b334136ab597cde52..fde833bac0f9f81e8536211b4dad6e7575c1219a 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -427,7 +427,7 @@ module_param(qovld, long, 0444); > > static ulong jiffies_till_first_fqs = ULONG_MAX; > > static ulong jiffies_till_next_fqs = ULONG_MAX; > > static bool rcu_kick_kthreads; > > -static int rcu_divisor = 7; > > +static int rcu_divisor = 6; > > module_param(rcu_divisor, int, 0644); > > > > /* Force an exit from rcu_do_batch() after 3 milliseconds. */ > > > > To be clear, you can adjust the value without building a new kernel. > > echo 6 >/sys/module/rcutree/parameters/rcu_divisor > I tried value 6, 5, and 4, but none of those removed the problem. Thanks, SeongJae Park