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 7E759C47256 for ; Tue, 5 May 2020 17:56:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E83E20752 for ; Tue, 5 May 2020 17:56:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="RppM4Sti" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730334AbgEER4t (ORCPT ); Tue, 5 May 2020 13:56:49 -0400 Received: from smtp-fw-33001.amazon.com ([207.171.190.10]:55852 "EHLO smtp-fw-33001.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729315AbgEER4t (ORCPT ); Tue, 5 May 2020 13:56:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1588701409; x=1620237409; h=from:to:cc:subject:date:message-id:in-reply-to: mime-version; bh=BZbaV+a4U8fFiIaIlrZCfbC3DcKGOdw37Xx/FKA1f8w=; b=RppM4StihQtn6BWRxdZ5FC5vrlO0lOo2yHzAPWMw5j1zVyqJ8QX+/Pgu Kllyrtlknn4NR0/6dFZ+UdUrx29imIgEJ7cJ9RvUZCP63Jv4XYe13r/n8 7Eplsekk3l+quNjNh7xMk2nB38auh+uzxQd8ZuxkhGTu12VagKoVBNSSG Y=; IronPort-SDR: G2mMMqyG1afU1/6i2loosHO4zzSo6fqmgFiJhpl6u0s8Jrh+UgW6IAkqpxpGXjZvRSSG9lLyVy BI0+yfKVsPzQ== X-IronPort-AV: E=Sophos;i="5.73,356,1583193600"; d="scan'208";a="42847329" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-1a-e34f1ddc.us-east-1.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-33001.sea14.amazon.com with ESMTP; 05 May 2020 17:56:47 +0000 Received: from EX13MTAUEA002.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan2.iad.amazon.com [10.40.159.162]) by email-inbound-relay-1a-e34f1ddc.us-east-1.amazon.com (Postfix) with ESMTPS id A6B97A1D89; Tue, 5 May 2020 17:56:43 +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 17:56:42 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.162.38) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 5 May 2020 17:56:35 +0000 From: SeongJae Park To: "Paul E. McKenney" CC: SeongJae Park , Eric Dumazet , Eric Dumazet , David Miller , "Al Viro" , Jakub Kicinski , "Greg Kroah-Hartman" , , netdev , LKML , SeongJae Park , , , Subject: Re: Re: Re: [PATCH net v2 0/2] Revert the 'socket_alloc' life cycle change Date: Tue, 5 May 2020 19:56:05 +0200 Message-ID: <20200505175605.12015-1-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200505173036.GE2869@paulmck-ThinkPad-P72> (raw) MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.43.162.38] X-ClientProxiedBy: EX13D18UWC004.ant.amazon.com (10.43.162.77) To EX13D31EUA001.ant.amazon.com (10.43.165.15) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 5 May 2020 10:30:36 -0700 "Paul E. McKenney" wrote: > On Tue, May 05, 2020 at 07:05:53PM +0200, SeongJae Park wrote: > > 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. > > Thank you for checking this! > > Was your earlier discussion on long RCU readers speculation, or do you > have measurements? It was just a guess without any measurement or dedicated investigation. Thanks, SeongJae Park > > Thanx, Paul