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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 5953BC433E2 for ; Tue, 23 Jun 2020 21:01:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3663620663 for ; Tue, 23 Jun 2020 21:01:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="oVFWJM2b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392189AbgFWVBQ (ORCPT ); Tue, 23 Jun 2020 17:01:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391290AbgFWVBN (ORCPT ); Tue, 23 Jun 2020 17:01:13 -0400 Received: from mail-qk1-x741.google.com (mail-qk1-x741.google.com [IPv6:2607:f8b0:4864:20::741]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21142C061755 for ; Tue, 23 Jun 2020 14:01:13 -0700 (PDT) Received: by mail-qk1-x741.google.com with SMTP id l6so16574282qkc.6 for ; Tue, 23 Jun 2020 14:01:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=IJiEAsm35OSf4Kwkxjuxcv6ZYgsjC9KkGStnrzjC88Y=; b=oVFWJM2bXi+g6I82oVYXQLlJ9lk1WSeyy3qQIY7hXM1+QNiyL941g9vTUMmMF2+NZj jO57gJMY8YB4KiVWgfaxBYL5R7ILDVFDX5GoulqsBQvOIyBuNRFYDjD4Tl3g70DrkOVQ FJDsY8GpK2/cuO9HayQAONyJQty6l81z3Zg5I= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=IJiEAsm35OSf4Kwkxjuxcv6ZYgsjC9KkGStnrzjC88Y=; b=QTTnFvHygvyZ3ez775LOhNQr4w/Jvmp6H6upTfl/SMoI7ebbCEEzgeOHpF4WveAYlZ kDaU0wf/4iCiCGfNNY9r46ZIsQByNaXvCqyPb54fxgVesgFYni0nsS61+3xvcIG8Fd1K 7gIeWhohD519Ghu2NNrY48Dh722rBaon2xJ4gPzHUTBbOZDJsx5W837W3wWXRSbTDRuC +tw28DaGAtV8cZUSi6fdxdS16afUMudw9XCAvEG1p9OlwiPIfd2CTIHMe7C8yk2Vp/hK ibXFvZ5Rh08b6kqUSSEhZHIG9sUnfquAzYp8l70VSgxxP6wyLZv8KkH2kVBL6dAILuGW 7NnA== X-Gm-Message-State: AOAM531hvdak4biWbmMr6C3dNLP04miXJEd/eHhNyJ5lyTmEK+ztayMZ VmOm+neEavo3/CmRIxH8w2eQdg== X-Google-Smtp-Source: ABdhPJyGfilx6CEztNReVMBgYC0n2g4vy+LYXCPCtYQvtlo+uVU0OgHhBU/jN8roRMjV0yw8NAAcyA== X-Received: by 2002:a37:9b04:: with SMTP id d4mr21002794qke.58.1592946072304; Tue, 23 Jun 2020 14:01:12 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id 185sm1595326qke.92.2020.06.23.14.01.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2020 14:01:11 -0700 (PDT) Date: Tue, 23 Jun 2020 17:01:11 -0400 From: Joel Fernandes To: "Paul E. McKenney" Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, linux-mm@kvack.org Subject: Re: [PATCH tip/core/rcu 02/26] mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls Message-ID: <20200623210111.GA117936@google.com> References: <20200623002128.GA25456@paulmck-ThinkPad-P72> <20200623002147.25750-2-paulmck@kernel.org> <20200623193431.GA68372@google.com> <20200623205508.GS9247@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200623205508.GS9247@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Tue, Jun 23, 2020 at 01:55:08PM -0700, Paul E. McKenney wrote: [..] > > Just for my understanding, cond_resched_tasks_rcu_qs() may not help here > > because preemption is not disabled right? Still I see no harm in using it > > here either as it may give a slight speed up for tasks-RCU. > > The RCU-tasks stall-warning interval is ten minutes, and I have not yet > seen evidence that we are getting close to that. If we do, then yes, > a cond_resched_tasks_rcu_qs() might be in this code's future. But it > does add overhead, so we need to see the evidence first. Yes, true about that overhead. Ok, this is fine with me too, thanks :) - Joel