From patchwork Thu Mar 9 09:31:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13167113 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95404C64EC4 for ; Thu, 9 Mar 2023 09:31:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230401AbjCIJba (ORCPT ); Thu, 9 Mar 2023 04:31:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230207AbjCIJb0 (ORCPT ); Thu, 9 Mar 2023 04:31:26 -0500 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7DD872B28 for ; Thu, 9 Mar 2023 01:31:23 -0800 (PST) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-536b7eb9117so14449677b3.14 for ; Thu, 09 Mar 2023 01:31:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1678354283; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=XmqAffVC+m+oVrrIAcB4LBUAdhmCJbGaOFJSOfA6Apk=; b=TFj7MTDsZpBNZ1Pa0nPpBjAVMapPhqIjEuIqItxSZfA4ak3MR9Zb48iIb7foczQpbX WbksQYQHrdZrln4nHdw6+5sdurXfjnbNe/kDD/0fdzYnrK4FPkh80+fXTAFYX+K7ErEh 1rcQSsoydEEK0CwMuckiZLK2zbAhv/zNi+QuBYMCZBwEZzkU8Itoiq8WU1TgB18gc2Bw EDGa5MXDFojPNO9J/WmuxVzK2IXT3yxoZSKw2S8SO1+F98jJAYgqAMtZYNYjCgHAsfK6 fm7hVlPreLuzvKK1gsnbhaUhDW/3kun5nSsDzOEnqh2wUc39UfeqzmXDz1CyRuaUl0uD IRvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678354283; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=XmqAffVC+m+oVrrIAcB4LBUAdhmCJbGaOFJSOfA6Apk=; b=OsJ4vheU5mK1KaionYSz0vz8AliCftnaF1VoHrHp3Hb1D6jSdh3EsxhaDsyl1gHAaG ow4Idy1DzbGaaINrYFVAg/DY4OWFDIGMQiSyOIbnkQXbJSIUTQbPkfv3qo/5tG8d44ae S3OtENCMbEbjUPcb7kGYSt7iNLwWuxdETP//sykedF7+lv2MjRHd7/E0b4o92zSd4Zfp 8nJWfXm5eEvesumVvmUVMIbt9m6IU4DPlelKB4vNVW5yrn3N1vXD8FrPcYTeaxDolNxq 1d3T3TP5w7EWXRqC+pcOIkMUC8T/bFsNBc8VbTDTQu+rBWGqz8cck4iFURTaHx32UdZD LX4g== X-Gm-Message-State: AO0yUKV82d1PlWmFgxwwUJ9YkHgL5dS/rV/7K/qbZwrozK//UhyOd6sC UMCCpKGgh2IYjMmTDg9KLSsRtg20TTYlF72J X-Google-Smtp-Source: AK7set8lfhDA1hmab01GBmCcbW1gNF0jJVZZ3P6U2WtB9nZ0L2Sl5efbx+XPbYy5GSpQU4+BOx2RAfHOQQ1GpTqg X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a25:fe04:0:b0:b1a:64ba:9c9b with SMTP id k4-20020a25fe04000000b00b1a64ba9c9bmr4212060ybe.1.1678354283152; Thu, 09 Mar 2023 01:31:23 -0800 (PST) Date: Thu, 9 Mar 2023 09:31:06 +0000 Mime-Version: 1.0 X-Mailer: git-send-email 2.40.0.rc0.216.gc4246ad0f0-goog Message-ID: <20230309093109.3039327-1-yosryahmed@google.com> Subject: [PATCH v2 0/3] Ignore non-LRU-based reclaim in memcg reclaim From: Yosry Ahmed To: Alexander Viro , "Darrick J. Wong" , Christoph Lameter , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Matthew Wilcox (Oracle)" , Miaohe Lin , David Hildenbrand , Johannes Weiner , Peter Xu , NeilBrown , Shakeel Butt , Michal Hocko , Yu Zhao Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Yosry Ahmed Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Upon running some proactive reclaim tests using memory.reclaim, we noticed some tests flaking where writing to memory.reclaim would be successful even though we did not reclaim the requested amount fully. Looking further into it, I discovered that *sometimes* we over-report the number of reclaimed pages in memcg reclaim. Reclaimed pages through other means than LRU-based reclaim are tracked through reclaim_state in struct scan_control, which is stashed in current task_struct. These pages are added to the number of reclaimed pages through LRUs. For memcg reclaim, these pages generally cannot be linked to the memcg under reclaim and can cause an overestimated count of reclaimed pages. This short series tries to address that. Patches 1-2 are just refactoring, they add helpers that wrap some operations on current->reclaim_state, and rename reclaim_state->reclaimed_slab to reclaim_state->reclaimed. Patch 3 ignores pages reclaimed outside of LRU reclaim in memcg reclaim. The pages are uncharged anyway, so even if we end up under-reporting reclaimed pages we will still succeed in making progress during charging. Do not let the diff stat deceive you, the core of this series is patch 3, which has one line of code change. All the rest is refactoring and one huge comment. v1 -> v2: - Renamed report_freed_pages() to mm_account_reclaimed_pages(), as suggested by Dave Chinner. There were discussions about leaving updating current->reclaim_state open-coded as it's not worth hiding the current dereferencing to remove one line, but I'd rather have the logic contained with mm/vmscan.c so that the next person that changes this logic doesn't have to change 7 different files. - Renamed add_non_vmscan_reclaimed() to flush_reclaim_state() (Johannes Weiner). - Added more context about how this problem was found in the cover letter (Johannes Weiner). - Added a patch to move set_task_reclaim_state() below the definition of cgroup_reclaim(), and added additional helpers in the same position. This way all the helpers for reclaim_state live together, and there is no need to declare cgroup_reclaim() early or move its definition around to call it from flush_reclaim_state(). This should also fix the build error reported by the bot in !CONFIG_MEMCG. RFC -> v1: - Exported report_freed_pages() in case XFS is built as a module (Matthew Wilcox). - Renamed reclaimed_slab to reclaim in previously missed MGLRU code. - Refactored using reclaim_state to update sc->nr_reclaimed into a helper and added an XL comment explaining why we ignore reclaim_state->reclaimed in memcg reclaim (Johannes Weiner). Yosry Ahmed (3): mm: vmscan: move set_task_reclaim_state() after cgroup_reclaim() mm: vmscan: refactor updating reclaimed pages in reclaim_state mm: vmscan: ignore non-LRU-based reclaim in memcg reclaim fs/inode.c | 3 +- fs/xfs/xfs_buf.c | 3 +- include/linux/swap.h | 5 ++- mm/slab.c | 3 +- mm/slob.c | 6 +-- mm/slub.c | 5 +-- mm/vmscan.c | 88 +++++++++++++++++++++++++++++++++++--------- 7 files changed, 81 insertions(+), 32 deletions(-)