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 CEDAAC2D0F3 for ; Wed, 1 Apr 2020 21:24:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A3E93206F6 for ; Wed, 1 Apr 2020 21:24:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585776261; bh=SpscMagTGAG+/VHvh41OMqrZQ5CvygLTC+B3GQz0ogk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=QOywTzsj0/8+4MLlneyISK9m5HUFK6N1+ajwuOeKvkptTS17BVWFzcX8uwn9aa1LR ukxcDETvCk8D94CYMejr+f8ylSbBbxobMasRjK5g2ippdpjcGcOGT14ZHzlWybGgik /8oYmXL90Kfx1IV6dgfym+ZwoCIvDlfVBnnYGDzY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732888AbgDAVYU (ORCPT ); Wed, 1 Apr 2020 17:24:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:60954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732357AbgDAVYU (ORCPT ); Wed, 1 Apr 2020 17:24:20 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 76EC7206F6; Wed, 1 Apr 2020 21:24:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585776259; bh=SpscMagTGAG+/VHvh41OMqrZQ5CvygLTC+B3GQz0ogk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=tVgRLcS2kdUtwBo1l6umHNb/ZLd3PjKyaifUwJ/xOhBSMlofuc0U1uiJgfN0BQpaG gp1Y+HCjgEV7x2MOKJKTAdIBFlQT+Fb4savqUbGMk/uYZnDwlc7VVE5a5U/eIl837P 2oq9+460OYha2qZ+/LKOXsVWJznHfv2y2T72cyC4= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 5243735226B3; Wed, 1 Apr 2020 14:24:19 -0700 (PDT) Date: Wed, 1 Apr 2020 14:24:19 -0700 From: "Paul E. McKenney" To: Uladzislau Rezki Cc: Joel Fernandes , linux-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: Re: What should we be doing to stress-test kfree_rcu()? Message-ID: <20200401212419.GN19865@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200401184415.GA7619@paulmck-ThinkPad-P72> <20200401205012.GC206273@google.com> <20200401211607.GA7531@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401211607.GA7531@pc636> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 01, 2020 at 11:16:07PM +0200, Uladzislau Rezki wrote: > On Wed, Apr 01, 2020 at 04:50:12PM -0400, Joel Fernandes wrote: > > On Wed, Apr 01, 2020 at 11:44:15AM -0700, Paul E. McKenney wrote: > > > Hello! > > > > > > What should we be doing to stress-test kfree_rcu(), including its ability > > > to cope with OOM conditions? Yes, rcuperf runs are nice, but they are not > > > currently doing much more than testing base functionality, performance, > > > and scalability. > > > > I already stress kfree_rcu() with rcuperf right now to a point of OOM and > > make sure it does not OOM. The way I do this is set my VM to low memory (like > > 512MB) and then flood kfree_rcu()s. After the shrinker changes, I don't see > > OOM with my current rcuperf settings. > > > > Not saying that my testing is sufficient, just saying this is what I do. It > > would be good to get a real workload to trigger lot of kfree_rcu() activity > > as well especially on low memory systems. Any ideas on that? > > > > One idea could be to trigger memory pressure from unrelated allocations (such > > as userspace memory hogs), and see how it perform with memory-pressure. For > > one, the shrinker should trigger in such situations to force the queue into > > waiting for a GP in such situations instead of batching too much. This would be good! > > We are also missing vmalloc() tests. I remember Vlad had some clever vmalloc > > tests around for his great vmalloc rewrites :). Vlad, any thoughts on getting > > to stress kvfree_rcu()? > > > Actually i updated(localy for my tests) the lib/test_vmalloc.c module with extra > test cases to stress kvfree_rcu() stuff. I think i should add them :) As would this! ;-) Thanx, Paul