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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 5BBC8C43331 for ; Thu, 5 Sep 2019 14:14:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D44D222BF for ; Thu, 5 Sep 2019 14:14:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="a2pBHK6e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731206AbfIEOOz (ORCPT ); Thu, 5 Sep 2019 10:14:55 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:35030 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729157AbfIEOOy (ORCPT ); Thu, 5 Sep 2019 10:14:54 -0400 Received: by mail-pg1-f195.google.com with SMTP id n4so1519572pgv.2 for ; Thu, 05 Sep 2019 07:14:54 -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:user-agent; bh=2dyh/qzhi2qens90CnAyZpu8nc1Cd1yi17MqcISR+xc=; b=a2pBHK6eVeP+DeXitzdhwlEvM99BkuEdPz9b/HbbIFuBRONPO0F/o6Um+dJ+WhLiki loBC03lOXyRmzxlQZn5Tub6me3ggBWFKOWP+jpBivc0UDj0Fuao3xzjPV3fWdHbmL60s bMR4jmepYzML3yWOff4TJnVSFSDkAhK0twfJk= 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:user-agent; bh=2dyh/qzhi2qens90CnAyZpu8nc1Cd1yi17MqcISR+xc=; b=U0lxyrJsh03inFn4W1pup+7RDfO33R+XaJZjDiGSICjXRAJzJIcFGx8rX+4ssYTUOw iC36roSdn2BNxJBXBGDXMm/4AIN834kK9zRLLXwwD+IRu4EDANtydmXdnuvnPqZynYkg Mib7ls3V726t02Zn16tgqs/fcO94ZZhjgFb24MZ6OXPbrdFJSjo6I0LF/IxoWXWj29Gm 1B6Y+XAfpkfDncCtdC/yHqN0Hf0qFfRjL1E9OEFMLqqPRYvgWienomodP720K0oPLr4K 8vb6Vob96f2+J5gUGQeL3VTbEEDsKe37WeaJjH3UwMcEYrz3O9zO13JZVdvjiQCi4z1C mUFg== X-Gm-Message-State: APjAAAWxa3q6BVI4rTXyL3GYXcfBGkvRY9FsHeOUhMaxbuDeQfip7lwn XedLw8nVSYnBk0y/0iKSlbMwYg== X-Google-Smtp-Source: APXvYqyWhg5wWBza0xoQXn734lb+BXrNSStNRVuCl14e2+JVF+qyGjoVQWM/ZfKFG0+uOaZkfe8M4w== X-Received: by 2002:a65:518a:: with SMTP id h10mr3310283pgq.117.1567692894079; Thu, 05 Sep 2019 07:14:54 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id l6sm8709786pje.28.2019.09.05.07.14.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Sep 2019 07:14:53 -0700 (PDT) Date: Thu, 5 Sep 2019 10:14:52 -0400 From: Joel Fernandes To: Michal Hocko 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: <20190905141452.GA26466@google.com> 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> <20190905105424.GG3838@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190905105424.GG3838@dhcp22.suse.cz> 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 On Thu, Sep 05, 2019 at 12:54:24PM +0200, Michal Hocko wrote: > 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: > > > > On Wed, Sep 04, 2019 at 10:45:08AM +0200, Michal Hocko wrote: > > > > > On Tue 03-09-19 16:09:05, Joel Fernandes (Google) wrote: > > > > > > Useful to track how RSS is changing per TGID to detect spikes in RSS and > > > > > > memory hogs. Several Android teams have been using this patch in various > > > > > > kernel trees for half a year now. Many reported to me it is really > > > > > > useful so I'm posting it upstream. > > > > > > > > > > > > Initial patch developed by Tim Murray. Changes I made from original patch: > > > > > > o Prevent any additional space consumed by mm_struct. > > > > > > o Keep overhead low by checking if tracing is enabled. > > > > > > o Add some noise reduction and lower overhead by emitting only on > > > > > > threshold changes. > > > > > > > > > > Does this have any pre-requisite? I do not see trace_rss_stat_enabled in > > > > > the Linus tree (nor in linux-next). > > > > > > > > No, this is generated automatically by the tracepoint infrastructure when a > > > > tracepoint is added. > > > > > > OK, I was not aware of that. > > > > > > > > Besides that why do we need batching in the first place. Does this have a > > > > > measurable overhead? How does it differ from any other tracepoints that we > > > > > have in other hotpaths (e.g. page allocator doesn't do any checks). > > > > > > > > We do need batching not only for overhead reduction, > > > > > > What is the overhead? > > > > The overhead is occasionally higher without the threshold (that is if we > > trace every counter change). I would classify performance benefit to be > > almost the same and within the noise. > > OK, so the additional code is not really justified. It is really justified. Did you read the whole of the last email? thanks, - Joel