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=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 0826AC2BA2B for ; Wed, 15 Apr 2020 04:39:16 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B22862078B for ; Wed, 15 Apr 2020 04:39:15 +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="ohUd4Clm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B22862078B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=cmpxchg.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 59C1C8E0005; Wed, 15 Apr 2020 00:39:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 54CC88E0001; Wed, 15 Apr 2020 00:39:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 462958E0005; Wed, 15 Apr 2020 00:39:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0125.hostedemail.com [216.40.44.125]) by kanga.kvack.org (Postfix) with ESMTP id 2C6B08E0001 for ; Wed, 15 Apr 2020 00:39:15 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id DF4D2181AEF1A for ; Wed, 15 Apr 2020 04:39:14 +0000 (UTC) X-FDA: 76708835028.08.magic34_50ab782491149 X-HE-Tag: magic34_50ab782491149 X-Filterd-Recvd-Size: 4408 Received: from mail-qt1-f193.google.com (mail-qt1-f193.google.com [209.85.160.193]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Wed, 15 Apr 2020 04:39:14 +0000 (UTC) Received: by mail-qt1-f193.google.com with SMTP id l13so9491184qtr.7 for ; Tue, 14 Apr 2020 21:39:14 -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=T0ov2Qm19NGfhDx7kb+Qpp+SBwZz53FIlhxAVVfKxI4=; b=ohUd4ClmbLBtja20CTalUO+WoLl1ve/CYr2CKbobL6GFJjNAc/LB440d9rYAIaczm+ Kh1RiX35n8e3voiqIitcaGFBnH91SfJlcl57iEyZB4hlEhvesoMX2eOXRdntSRzr+hkH dOgBVJDAi3bFtryful1Kxe6qHJjkhz8LI+/jrG88Tceh+0BEVEYbpFpYF0ghcHG85Bds xGbea9oZ/UqbxOf2r/VOb2z4UXNriOnt8vLpgXJTQ3e/vG7ky2SV4TLQSwKYnh7deLwR oAwhiU7x7YTEH6UiJ6nFbWPhGeJ7/i28lQNYphRYEI0IgJ7Lpo8+wtqijJbG7rp5t8sG Io+w== 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=T0ov2Qm19NGfhDx7kb+Qpp+SBwZz53FIlhxAVVfKxI4=; b=skFqt4X5cUNPHkSUBubKcCYO55chFj75yM4S8u4WQGqkNjdGPL+s77/ONIG2II9Ox+ ZskyY9LqRBwOleeBULmBPX/QYH+wgaeV3u1LbOXtzZMNHogoB1vDUHu03lu9MK0y37E8 rSMkDP5CmisaeCjvVJAbI3FiunRXWaVcmH1kU0aHlxL8G1dOmtp1YuSxeoKKcYcqrLev RWKepUWPDOM8QB2OAgmBRZYD6/zcFFflsjWi9FwJeZi8uKDOJNx4bEvVc3L7IGk5a1pX CyO42YDk+qQPLprBgHMYDzRZcO1U/GG7qz4UiCVhpoOwvqRCfnHU8nQ8r1vZXjcPHzSA 8rCQ== X-Gm-Message-State: AGi0PuZsWlPcxcpSlL6JH4dWKKWfE+4pdG+0nbIXLZCiLeflapVoINsk KcJiXGDgcTyeriLT6XWbHD1MLg== X-Google-Smtp-Source: APiQypIM5GoBSgbWbxjSMNs5ZNvz31Ab4J1vE8UwPpZfVZ7JsFAzFEaxoKJVsfy/rFJmxjNa4l9+dw== X-Received: by 2002:ac8:543:: with SMTP id c3mr18876077qth.8.1586925553554; Tue, 14 Apr 2020 21:39:13 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::e623]) by smtp.gmail.com with ESMTPSA id i56sm5581998qte.6.2020.04.14.21.39.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2020 21:39:12 -0700 (PDT) Date: Wed, 15 Apr 2020 00:39:11 -0400 From: Johannes Weiner To: Chris Down Cc: Andrew Morton , Jakub Kicinski , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH] mm, memcg: Do not high throttle allocators based on wraparound Message-ID: <20200415043911.GA147015@cmpxchg.org> References: <20200331152424.GA1019937@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200331152424.GA1019937@chrisdown.name> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000069, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 31, 2020 at 04:24:24PM +0100, Chris Down wrote: > From: Jakub Kicinski > > If a cgroup violates its memory.high constraints, we may end > up unduly penalising it. For example, for the following hierarchy: > > A: max high, 20 usage > A/B: 9 high, 10 usage > A/C: max high, 10 usage > > We would end up doing the following calculation below when calculating > high delay for A/B: > > A/B: 10 - 9 = 1... > A: 20 - PAGE_COUNTER_MAX = 21, so set max_overage to 21. > > This gets worse with higher disparities in usage in the parent. > > I have no idea how this disappeared from the final version of the patch, > but it is certainly Not Good(tm). This wasn't obvious in testing > because, for a simple cgroup hierarchy with only one child, the result > is usually roughly the same. It's only in more complex hierarchies that > things go really awry (although still, the effects are limited to a > maximum of 2 seconds in schedule_timeout_killable at a maximum). > > [chris@chrisdown.name: changelog] > > Fixes: e26733e0d0ec ("mm, memcg: throttle allocators based on ancestral memory.high") > Signed-off-by: Jakub Kicinski > Signed-off-by: Chris Down > Cc: Johannes Weiner > Cc: stable@vger.kernel.org # 5.4.x Oops. Acked-by: Johannes Weiner