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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29A56C7619A for ; Tue, 11 Apr 2023 23:48:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8505A900002; Tue, 11 Apr 2023 19:48:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7FF006B0075; Tue, 11 Apr 2023 19:48:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6C714900002; Tue, 11 Apr 2023 19:48:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 5930A6B0074 for ; Tue, 11 Apr 2023 19:48:52 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 26B621C5C21 for ; Tue, 11 Apr 2023 23:48:52 +0000 (UTC) X-FDA: 80670752904.15.8D4B5A3 Received: from mail-ed1-f41.google.com (mail-ed1-f41.google.com [209.85.208.41]) by imf27.hostedemail.com (Postfix) with ESMTP id 610E84001A for ; Tue, 11 Apr 2023 23:48:50 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=qDjRrSVe; spf=pass (imf27.hostedemail.com: domain of yosryahmed@google.com designates 209.85.208.41 as permitted sender) smtp.mailfrom=yosryahmed@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1681256930; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xoyQVeaFsgpeGhfzOdZSPoa4a8w+FT9SRbAgSywf7sc=; b=C5TT9Q8qnQbEtK/wsJEWmGreMdnwzeYFtm+vu2YAAH+CPC6du/o3+PlblznqwjNxLTiqbp a8crL+TcZvelZX/8Ty6NWc0sbqhtJCxoYqc9MmPzel+z2EQu0aePjsuXhmOKkVxOUJwF8Z EOGvcb9/7UW9vU640/Fy3KckKwF4Cik= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=qDjRrSVe; spf=pass (imf27.hostedemail.com: domain of yosryahmed@google.com designates 209.85.208.41 as permitted sender) smtp.mailfrom=yosryahmed@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1681256930; a=rsa-sha256; cv=none; b=bKzTHDij5h5V1rOHU1Q27ztnAaFwr9Rp0IryC/zImySuDyUnLYJgB/XXNykDXNEkkEAyiy Q6+H+jdlwgkYDUM0zm7q4hRxQshfZ9LEjja8G+yRV6GVrHDG87ELnoWKIGTU6UX91bh47h epLgfZYvzqkWWtnVEOrBlHm+o11jkqs= Received: by mail-ed1-f41.google.com with SMTP id 4fb4d7f45d1cf-50489c109f4so2672283a12.2 for ; Tue, 11 Apr 2023 16:48:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1681256929; x=1683848929; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=xoyQVeaFsgpeGhfzOdZSPoa4a8w+FT9SRbAgSywf7sc=; b=qDjRrSVe7rsc75FviosB6qBZZ8fCZ27cRjYKQggjvqCGoWu4bJAUH/sIetxt+jzJmA C9SIxTBxB4l4i/l8YBaF/G4nsjyQj4fLt+nst3hlwnb76omBpv+cgdFVmcsgGIPpzEe8 kPANJ5G/LZzwI2nbaWbd5sCf7GJX4TkHJKdcoey1qCE3RRRT3fG+f++YWyLHngRa6OA0 GGOzSZDP0zNup7QsE8n2/iT33pRTx7h89PnzZyF5K/DNwnlY3syA43611ydty5JEeTYe lIkyLa9naq08kcgIbNf0WqfSC50meamQ5Veq+kczO7cHl5BDnXd2a4kHWujmddiHMSeT HVLw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1681256929; x=1683848929; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=xoyQVeaFsgpeGhfzOdZSPoa4a8w+FT9SRbAgSywf7sc=; b=bm7os1nV0M2Inj8BLEDKQIyY0HxFtzbH2iDMWxfckUlF5GzXSr4sZOP/r7n+IUsQ5I myEnlgkU0VmXdJJurDXXFkKgH40uEs81hrAfM83qULrWwyLeazZo+wK6+sfMFR7dVgFr Y1sx7xR/Zu59NTP8ItleR30g2o/+pZxEu7Aez5OuvzOZvS0tndNILR7PV+EJEyEfmywO RoaOePRlt9rU2bKSSXSB9A217GDr+LXQ7U7jF1UC+IQz7cu1+z2NjYN0UBR22+jFlUAK RnfJaEesnOOT6zFnbC7l+o6vw+yGDmKw18rxP3ZL7toPsCOFXmyaCGYlxlPgyMgOFm3d IKpg== X-Gm-Message-State: AAQBX9dWXQMjsczx9Q/qzV+0L6ayNQRKl7y27yelJ+yfw/P2XB+yvawG eONinWyrr8clWt6BhItjJSiGw4y8YP25Aj2QMwmjDA== X-Google-Smtp-Source: AKy350aZHW00zKNbOfPWEMuywutfcfS3WFGXLIvU+WGuLxH7vQzLyshmSGH8jpwUKpfgctR2eUf/owFlFW5x9NG6o1Y= X-Received: by 2002:a50:cddc:0:b0:4fb:9735:f915 with SMTP id h28-20020a50cddc000000b004fb9735f915mr7538990edj.8.1681256928740; Tue, 11 Apr 2023 16:48:48 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Yosry Ahmed Date: Tue, 11 Apr 2023 16:48:12 -0700 Message-ID: Subject: Re: [LSF/MM/BPF TOPIC] Reducing zombie memcgs To: "T.J. Mercier" Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, cgroups@vger.kernel.org, Tejun Heo , Shakeel Butt , Muchun Song , Johannes Weiner , Roman Gushchin , Alistair Popple , Jason Gunthorpe , Kalesh Singh , Yu Zhao Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 610E84001A X-Stat-Signature: d63dptio41mzzrhqim3kcynt8ts7o59f X-HE-Tag: 1681256930-61187 X-HE-Meta: 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 iVJuD02S qeRW6zh9kL5Uv1zXNKvQbMsSiiKQge2zmSbzDrA6CFk8jde8yrV+jwPisgnk5iKn/KKz1vBDipvR0Zdc7HiZPCz0cWecU803o12CgKcbTvpSjPtwZEqqFeldA/AbKBx8nd0E9iPd9qWxaaHxOb38RwyANq5ZZk9rOYJO4aEu0NKKWXGroh+TXdq7W8ANdmUPZjHOfpAU0egE26XFQJiGAx9/g/Y8BEM3giTwOFBOx0kvs5qgZ/NlUFljqCEh1gdYZwEn0eAQibEVYgZzLrqfQSlDTBX+M2/iLOyjurU5u8P3yuEoEAMBvKGLlplw5Y/FilygDu4FY3Wgc2LAufdox8ydooFhJeGOAdGBIlvIV+aAg9gn7KBBNGb9KRXMejsjdLrr/gJKC8ung5tmG0PxmyiwFoQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 11, 2023 at 4:36=E2=80=AFPM T.J. Mercier = wrote: > > When a memcg is removed by userspace it gets offlined by the kernel. > Offline memcgs are hidden from user space, but they still live in the > kernel until their reference count drops to 0. New allocations cannot > be charged to offline memcgs, but existing allocations charged to > offline memcgs remain charged, and hold a reference to the memcg. > > As such, an offline memcg can remain in the kernel indefinitely, > becoming a zombie memcg. The accumulation of a large number of zombie > memcgs lead to increased system overhead (mainly percpu data in struct > mem_cgroup). It also causes some kernel operations that scale with the > number of memcgs to become less efficient (e.g. reclaim). > > There are currently out-of-tree solutions which attempt to > periodically clean up zombie memcgs by reclaiming from them. However > that is not effective for non-reclaimable memory, which it would be > better to reparent or recharge to an online cgroup. There are also > proposed changes that would benefit from recharging for shared > resources like pinned pages, or DMA buffer pages. I am very interested in attending this discussion, it's something that I have been actively looking into -- specifically recharging pages of offlined memcgs. > > Suggested attendees: > Yosry Ahmed > Yu Zhao > T.J. Mercier > Tejun Heo > Shakeel Butt > Muchun Song > Johannes Weiner > Roman Gushchin > Alistair Popple > Jason Gunthorpe > Kalesh Singh