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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 68DD7C43331 for ; Thu, 5 Sep 2019 14:43:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C6AE206BA for ; Thu, 5 Sep 2019 14:43:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567694594; bh=Be2GZJp0KKr2/w+lQ1U7ppjQgyQjZbokUIubYRKfjyY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=GL5iabsuGBrDI7eIKIgcl0XM2JKKy6BvxTmeHCIO5ZTqfKC0Wqdz4jB9Cj6VhCQBs lijtgiKKin6oU6cVvDCBJbZ2SnPP7GMCfW3AEPCLwOnhQiC7ao9a5QKMBLhEK1iR3e /HE0SvAohM57VfsncDO7FY+3dXhccHmWkWtB460A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389730AbfIEOnN (ORCPT ); Thu, 5 Sep 2019 10:43:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:37644 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726080AbfIEOnN (ORCPT ); Thu, 5 Sep 2019 10:43:13 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id ABAC9B0BA; Thu, 5 Sep 2019 14:43:11 +0000 (UTC) Date: Thu, 5 Sep 2019 16:43:10 +0200 From: Michal Hocko To: Joel Fernandes , Steven Rostedt Cc: linux-kernel@vger.kernel.org, Tim Murray , carmenjackson@google.com, mayankgupta@google.com, dancol@google.com, rostedt@goodmis.org, minchan@kernel.org, akpm@linux-foundation.org, kernel-team@android.com, "Aneesh Kumar K.V" , Dan Williams , Jerome Glisse , linux-mm@kvack.org, Matthew Wilcox , Ralph Campbell , Vlastimil Babka Subject: Re: [PATCH v2] mm: emit tracepoint when RSS changes by threshold Message-ID: <20190905144310.GA14491@dhcp22.suse.cz> References: <20190903200905.198642-1-joel@joelfernandes.org> <20190904084508.GL3838@dhcp22.suse.cz> <20190904153258.GH240514@google.com> <20190904153759.GC3838@dhcp22.suse.cz> <20190904162808.GO240514@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190904162808.GO240514@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Add Steven] On Wed 04-09-19 12:28:08, Joel Fernandes wrote: > On Wed, Sep 4, 2019 at 11:38 AM Michal Hocko wrote: > > > > On Wed 04-09-19 11:32:58, Joel Fernandes wrote: [...] > > > but also for reducing > > > tracing noise. Flooding the traces makes it less useful for long traces and > > > post-processing of traces. IOW, the overhead reduction is a bonus. > > > > This is not really anything special for this tracepoint though. > > Basically any tracepoint in a hot path is in the same situation and I do > > not see a point why each of them should really invent its own way to > > throttle. Maybe there is some way to do that in the tracing subsystem > > directly. > > I am not sure if there is a way to do this easily. Add to that, the fact that > you still have to call into trace events. Why call into it at all, if you can > filter in advance and have a sane filtering default? > > The bigger improvement with the threshold is the number of trace records are > almost halved by using a threshold. The number of records went from 4.6K to > 2.6K. Steven, would it be feasible to add a generic tracepoint throttling? -- Michal Hocko SUSE Labs