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 37C7BC32771 for ; Wed, 15 Jan 2020 22:45:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05B572053B for ; Wed, 15 Jan 2020 22:45:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="r5V5pidG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730814AbgAOWpo (ORCPT ); Wed, 15 Jan 2020 17:45:44 -0500 Received: from mail-pg1-f194.google.com ([209.85.215.194]:39737 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729548AbgAOWpo (ORCPT ); Wed, 15 Jan 2020 17:45:44 -0500 Received: by mail-pg1-f194.google.com with SMTP id b137so8880418pga.6 for ; Wed, 15 Jan 2020 14:45:44 -0800 (PST) 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=2E4ZVUUfLbzpLrVBEB+deJES/rw45hxzAWWuIoxmTL8=; b=r5V5pidGXOJVHi9WCUNRSyKfZQNzn2Az0BwDRgA3qaBi6+AfYKt3KVJ5Eg/6kggpFF q1RNL1lnq9le+u4d4Sl1fPqGgZXwkAGgzzrV0tjj8Ma+qrhIJqjqGtegLW3UvKBTclw5 jb7vwOhPrfiZr5qlsXN1PIfsrcr1mPRx9JHIU= 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=2E4ZVUUfLbzpLrVBEB+deJES/rw45hxzAWWuIoxmTL8=; b=Wn1DCujv1PUHgZX72b2O95skJb3WUAdcAwgVcFNqHoMPqBJzhIpU4hpsVzWoTxQ3XI gQ2Ihsma08rWrodHI6ehl1zcA5lqxcXTgtNs+SrecbnDvNziIBmlK8WkW/79j1UsWjeY a3ELs4hZW1rpXtsUv4P7lCijjVdMPCJ4lGmakpaTHAaKonxY2tQlHvLivisvWuuWlv4/ 2B5OFddkqWELVZSaZcP/qpmUY/glLwYi1k4GfDwIqms4s4oaePe9U1l8ptMq8lp60kwH 31e+xpRC/WUqoxUX1Qz+nSNY/V+HQagvUYizvTY6cNmD76ub3y8bxoLN/j+gvLZ5xpGm s1cw== X-Gm-Message-State: APjAAAW8/vl3htI4GZ0JYVMju7dh5T4EUjwmBfHR8FmMSzOvY5TJDk+5 opBXjO+HYQ2HOt1kqf1gwRUeScLQVBU= X-Google-Smtp-Source: APXvYqzteva7NK73fn8eM2ETrJHg0uJ/CJGFnPvaoFG0ne8N1doNSANgs5bfgCEHcpwVumccS01Apg== X-Received: by 2002:a62:8602:: with SMTP id x2mr34085776pfd.39.1579128344007; Wed, 15 Jan 2020 14:45:44 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id j2sm22623663pfi.22.2020.01.15.14.45.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2020 14:45:43 -0800 (PST) Date: Wed, 15 Jan 2020 17:45:42 -0500 From: Joel Fernandes To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, bristot@redhat.com, frextrite@gmail.com, madhuparnabhowmik04@gmail.com, urezki@gmail.com, Davidlohr Bueso , Josh Triplett , Lai Jiangshan , Mathieu Desnoyers , rcu@vger.kernel.org, Steven Rostedt Subject: Re: [PATCH v3 rcu-dev] rcuperf: Measure memory footprint during kfree_rcu() test Message-ID: <20200115224542.GB94036@google.com> References: <20191219211349.235877-1-joel@joelfernandes.org> <20191221000729.GH2889@paulmck-ThinkPad-P72> <20191221033714.GB156579@google.com> <20200106195200.GS13449@paulmck-ThinkPad-P72> <20200115220300.GA94036@google.com> <20200115224251.GK2935@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200115224251.GK2935@paulmck-ThinkPad-P72> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Wed, Jan 15, 2020 at 02:42:51PM -0800, Paul E. McKenney wrote: > > [snip] > > > > We can certainly refine it further but at this time I am thinking of spending > > > > my time reviewing Lai's patches and learning some other RCU things I need to > > > > catch up on. If you hate this patch too much, we can also defer this patch > > > > review for a bit and I can carry it in my tree for now as it is only a patch > > > > to test code. But honestly, in its current form I am sort of happy with it. > > > > > > OK, I will keep it as is for now and let's look again later on. It is not > > > in the bucket for the upcoming merge window in any case, so we do have > > > quite a bit of time. > > > > > > It is not that I hate it, but rather that I want to be able to give > > > good answers to questions that might come up. And given that I have > > > occasionally given certain people a hard time about their statistics, > > > it is only reasonable to expect them to return the favor. I wouldn't > > > want you to be caught in the crossfire. ;-) > > > > Since the weights were concerning, I was thinking of just using a weight of > > (1 / N) where N is the number of samples. Essentially taking the average. > > That could be simple enough and does not cause your concerns with weight > > tuning. I tested it and looks good, I'll post it shortly. > > YES!!! ;-) > > Snapshot mem_begin before entering the loop. For the mean value to > be solid, you need at least 20-30 samples, which might mean upping the > default for kfree_loops. Have an "unsigned long long" to accumulate the > sum, which should avoid any possibility of overflow for current systems > and for all systems for kfree_loops less than PAGE_SIZE. At which point, > forget the "%" stuff and just sum up the si_mem_available() on each pass > through the loop. > > Do the division on exit from the loop, preferably checking for divide > by zero. > > Straightforward, fast, reasonably reliable, and easy to defend. I mostly did it along these lines. Hopefully the latest posting is reasonable enough ;-) I sent it twice because I messed up the authorship (sorry). thanks, - Joel