From patchwork Tue Feb 28 08:50:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13154532 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 E1045C64ED6 for ; Tue, 28 Feb 2023 08:50:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229561AbjB1Iud (ORCPT ); Tue, 28 Feb 2023 03:50:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230492AbjB1IuS (ORCPT ); Tue, 28 Feb 2023 03:50:18 -0500 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 874151A96C for ; Tue, 28 Feb 2023 00:50:10 -0800 (PST) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-5376fa4106eso197505577b3.7 for ; Tue, 28 Feb 2023 00:50:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1677574209; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=th38ntbA4Oc2oiVVTEFN7kVCZXMfBHW5bqzoJX/NKxM=; b=Qx1HMjnOH9OsA3ycuQn28p/IaZ+Hp3kNuLp2QUi9h0Ycfnoty+yQNpg+WRxNuY/vYp jOY7XFohXtJylm8Zhy5PNGpA0U7IS0oAfCING0t+nz1L/hwrLlAjdn6QB4BQ7g4vN6HH OAiYlZHTTmYK4E/ibEh6T98sf4VZmgYow+qhvCLJm9G0PRCymGehRtI1hbaEgguuPSwP c7t1cNU/lIriIMXf5vdSZTLjo71hA+1rjgeHrdym+NEDcQOTi8Gy7EZ3GPG7NMQg7zho MG8uusZE7ELVwRFmlhIaXFZ9jTXMsB870R8rLfTvIx/zMtY4Y5kaKuhA8atMfdGBrjnt RIMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1677574209; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=th38ntbA4Oc2oiVVTEFN7kVCZXMfBHW5bqzoJX/NKxM=; b=JiKPs1vZM4QvYm5UMXFuPbYp96r8PqwyIMyyJXNhpdcsFLKEjmKEZ/cLPG78rA8xU3 YK3j8/YtbzMoZd1bEbrtxrAsR9XcFEix/ydfI8S4c3M0KJEam4EZtLeGeD3vOx8lNsYB Ci9nZTPS88iJGd4DPNt0iApbdkDk0i5/5JkFNhmZ4RDfNFhQU1ob0j+HDDjnmZNzIWQQ obpimWoDyDOVPckvgUxEuIeeWNfBaQeBMKCneCiY9CaBbYZTtYF0saR7/bKfQNBETiS7 LmFsteeUue6iSRTzXltl48nNmNmKIQKS7F3nlO8r1NNWBfxxcaCzw04uCk5hQxzMBm0P 6qpw== X-Gm-Message-State: AO0yUKV8m3cjy7rYl3FMOHfe+uGPQZLV5WXTIN6ljHwM28YiHWZueQ9n DdQdEIi4ImJ3+12sMqQ94EQUzckyjtIxHUAa X-Google-Smtp-Source: AK7set+DvIV3bw19wB6Hwqeb1fxI1Ob9E6fp4FkYQsDq5MINr8X9kGIXdnH2rMDNI8ge0fm/8/tJGYKLqoW41WxG X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a81:ad67:0:b0:525:2005:7dc2 with SMTP id l39-20020a81ad67000000b0052520057dc2mr1184169ywk.1.1677574209698; Tue, 28 Feb 2023 00:50:09 -0800 (PST) Date: Tue, 28 Feb 2023 08:50:02 +0000 In-Reply-To: <20230228085002.2592473-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230228085002.2592473-1-yosryahmed@google.com> X-Mailer: git-send-email 2.39.2.722.g9855ee24e9-goog Message-ID: <20230228085002.2592473-3-yosryahmed@google.com> Subject: [PATCH v1 2/2] mm: vmscan: 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 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 We keep track of different types of reclaimed pages through reclaim_state->reclaimed, and we add them to the reported number of reclaimed pages. For non-memcg reclaim, this makes sense. For memcg reclaim, we have no clue if those pages are charged to the memcg under reclaim. Slab pages are shared by different memcgs, so a freed slab page may have only been partially charged to the memcg under reclaim. The same goes for clean file pages from pruned inodes (on highmem systems) or xfs buffer pages, there is no way to link them to the memcg under reclaim. Stop reporting those freed pages as reclaimed pages during memcg reclaim. This should make the return value of writing to memory.reclaim, and may help reduce unnecessary reclaim retries during memcg charging. Generally, this should make the return value of try_to_free_mem_cgroup_pages() more accurate. In some limited cases (e.g. freed a slab page that was mostly charged to the memcg under reclaim), the return value of try_to_free_mem_cgroup_pages() can be underestimated, but this should be fine. The freed pages will be uncharged anyway, and we can charge the memcg the next time around as we usually do memcg reclaim in a retry loop. Signed-off-by: Yosry Ahmed --- mm/vmscan.c | 50 +++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 39 insertions(+), 11 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 8846531e85a4..c53659221965 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -188,6 +188,16 @@ struct scan_control { */ int vm_swappiness = 60; +static bool cgroup_reclaim(struct scan_control *sc) +{ + return sc->target_mem_cgroup; +} + +static bool global_reclaim(struct scan_control *sc) +{ + return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup); +} + static void set_task_reclaim_state(struct task_struct *task, struct reclaim_state *rs) { @@ -217,7 +227,35 @@ EXPORT_SYMBOL(report_freed_pages); static void add_non_vmscan_reclaimed(struct scan_control *sc, struct reclaim_state *rs) { - if (rs) { + /* + * Currently, reclaim_state->reclaimed includes three types of pages + * freed outside of vmscan: + * (1) Slab pages. + * (2) Clean file pages from pruned inodes. + * (3) XFS freed buffer pages. + * + * For all of these cases, we have no way of finding out whether these + * pages were related to the memcg under reclaim. For example, a freed + * slab page could have had only a single object charged to the memcg + * under reclaim. Also, populated inodes are not on shrinker LRUs + * anymore except on highmem systems. + * + * Instead of over-reporting the reclaimed pages in a memcg reclaim, + * only count such pages in system-wide reclaim. This prevents + * unnecessary retries during memcg charging and false positive from + * proactive reclaim (memory.reclaim). + * + * For uncommon cases were the freed pages were actually significantly + * charged to the memcg under reclaim, and we end up under-reporting, it + * should be fine. The freed pages will be uncharged anyway, even if + * they are not reported properly, and we will be able to make forward + * progress in charging (which is usually in a retry loop). + * + * We can go one step further, and report the uncharged objcg pages in + * memcg reclaim, to make reporting more accurate and reduce + * under-reporting, but it's probably not worth the complexity for now. + */ + if (rs && !cgroup_reclaim(sc)) { sc->nr_reclaimed += rs->reclaimed; rs->reclaimed = 0; } @@ -463,16 +501,6 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg) up_read(&shrinker_rwsem); } -static bool cgroup_reclaim(struct scan_control *sc) -{ - return sc->target_mem_cgroup; -} - -static bool global_reclaim(struct scan_control *sc) -{ - return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup); -} - /** * writeback_throttling_sane - is the usual dirty throttling mechanism available? * @sc: scan_control in question