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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 A73C1C433DF for ; Tue, 18 Aug 2020 13:50:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 835F520888 for ; Tue, 18 Aug 2020 13:50:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cmpxchg-org.20150623.gappssmtp.com header.i=@cmpxchg-org.20150623.gappssmtp.com header.b="gFo2tdrj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726763AbgHRNuQ (ORCPT ); Tue, 18 Aug 2020 09:50:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726451AbgHRNuO (ORCPT ); Tue, 18 Aug 2020 09:50:14 -0400 Received: from mail-qt1-x842.google.com (mail-qt1-x842.google.com [IPv6:2607:f8b0:4864:20::842]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB6DEC061389 for ; Tue, 18 Aug 2020 06:50:13 -0700 (PDT) Received: by mail-qt1-x842.google.com with SMTP id t23so15130729qto.3 for ; Tue, 18 Aug 2020 06:50:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=i3gzOAPUdUUgkW+MfJiRBZzylD1SwKDup35ranLTE+8=; b=gFo2tdrjm1qkUJWuDiFskzbeO0w5LJx6dyzsZOPwPfOmHDSXzdBGEcXIwDX7whrNV9 JEgVlPiTxZyMBirBuYCHGck9cYWCBQmt5ny0jayeNQ6gfZp4LNLHaLYVZRHrSHKeUY6e uRSpvrjdgx5mqhJbaHjlzb+ptaePm6k7omgqsuP3hL/1RmdPdVTPoALIZZdr5eyJ54WL dsftHxbUTIR9tXIDvqG8jN4H2/lH+Rf1hR50Z0vtfC6A7sLoLgtiM/v15If1BpTZRwDI SAX24oCanz2Ny6U8qxDU6UGtpXs/jD/FGeqLm7SIrw5GSVnzTYUHBo7UfMACrG1lFPPe a1mA== 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=i3gzOAPUdUUgkW+MfJiRBZzylD1SwKDup35ranLTE+8=; b=RAC1G9CELsG9jp7d7uH1N0rX9/X9OnXMJniNRaSi/4mT3Fiw0YVhRpmJzQ53bEY5fg 2uHnNrMzMV1KtMnZUPkf/hR4wKEJAudziNqrl/vJwAL9VZuCLNg+q7nKj97luMvxWiTU p2DH8ffj8dr6a9cAx8AfSgYkBw8IEknLhU0I5u+SmcJgARaXsXMLmzdL2PpmtHE6t0b+ 6gedfCsyXg5EPPzsdXLtb/n9aBT0S7CIHZiXiQq/2KZs0X+Q0NsWMIHmJaTdaEfO+xUn lhWJMYGMFXEzD7Tu/0eIeJtNWEOMVliDUhuoTvhmQm9aSFxwFyfnNBOConMMv+1eilGo tPRQ== X-Gm-Message-State: AOAM531SiJvkOrTnVHVEOv7ewyas4Jt7bsw+RBV4CEoihIh9rO4oSEgv 7wTIZvMNP5JoBRc/qe3+tkmelQ== X-Google-Smtp-Source: ABdhPJw0MsM7i8bwRZrEdghN116s3dEIEMDqeIJ6VBf7FQiar70mWUPczCEi3eXDG6n3hDEhYsCK4w== X-Received: by 2002:ac8:368f:: with SMTP id a15mr18218469qtc.288.1597758612969; Tue, 18 Aug 2020 06:50:12 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::1:8b3]) by smtp.gmail.com with ESMTPSA id n15sm20639882qkk.28.2020.08.18.06.50.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Aug 2020 06:50:11 -0700 (PDT) Date: Tue, 18 Aug 2020 09:49:00 -0400 From: Johannes Weiner To: peterz@infradead.org Cc: Michal Hocko , Waiman Long , Andrew Morton , Vladimir Davydov , Jonathan Corbet , Alexey Dobriyan , Ingo Molnar , Juri Lelli , Vincent Guittot , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 0/8] memcg: Enable fine-grained per process memory control Message-ID: <20200818134900.GA829964@cmpxchg.org> References: <20200817140831.30260-1-longman@redhat.com> <20200818091453.GL2674@hirez.programming.kicks-ass.net> <20200818092617.GN28270@dhcp22.suse.cz> <20200818095910.GM2674@hirez.programming.kicks-ass.net> <20200818100516.GO28270@dhcp22.suse.cz> <20200818101844.GO2674@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200818101844.GO2674@hirez.programming.kicks-ass.net> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Aug 18, 2020 at 12:18:44PM +0200, peterz@infradead.org wrote: > What you need is a feeback loop against the rate of freeing pages, and > when you near the saturation point, the allocation rate should exactly > match the freeing rate. IO throttling solves a slightly different problem. IO occurs in parallel to the workload's execution stream, and you're trying to take the workload from dirtying at CPU speed to rate match to the independent IO stream. With memory allocations, though, freeing happens from inside the execution stream of the workload. If you throttle allocations, you're most likely throttling the freeing rate as well. And you'll slow down reclaim scanning by the same amount as the page references, so it's not making reclaim more successful either. The alloc/use/free (im)balance is an inherent property of the workload, regardless of the speed you're executing it at. So the goal here is different. We're not trying to pace the workload into some form of sustainability. Rather, it's for OOM handling. When we detect the workload's alloc/use/free pattern is unsustainable given available memory, we slow it down just enough to allow userspace to implement OOM policy and job priorities (on containerized hosts these tend to be too complex to express in the kernel's oom scoring system). The exponential curve makes it look like we're trying to do some type of feedback system, but it's really only to let minor infractions pass and throttle unsustainable expansion ruthlessly. Drop-behind reclaim can be a bit bumpy because we batch on the allocation side as well as on the reclaim side, hence the fuzz factor there.