From patchwork Tue Apr 4 00:13:53 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13198929 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 5D3A0C76188 for ; Tue, 4 Apr 2023 00:14:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231906AbjDDAOQ (ORCPT ); Mon, 3 Apr 2023 20:14:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231741AbjDDAOE (ORCPT ); Mon, 3 Apr 2023 20:14:04 -0400 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47CFF4229 for ; Mon, 3 Apr 2023 17:14:02 -0700 (PDT) Received: by mail-pj1-x104a.google.com with SMTP id ie7-20020a17090b400700b0023f06808981so8021137pjb.8 for ; Mon, 03 Apr 2023 17:14:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680567242; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=QYyKpmgAe3S55Nk5FWRs2dH0UIocesat7xjNxdFTU4k=; b=W5WukSX7xVU0/vv5ALD+tup9Pddeb9Iipi9kb8kJt/jBn+TQTiZoJyEWgKO/OQ61Jh 2tDeM9kRzvnDYGPtmMlhz5iVehjZJg/jQ63YFUQ7WbbPKq0AY2cM2cHrwogahpd+PgEG XwtqC+dGnvs0z0/3t8FCcMDB2O7fMVf3H3E2qFVcjwb9hPLZO3zgEa2XrTMXRi9MFCHf WEtCE6c9sD8f7AqxvmgV8c+yt8qmrF2I9lAqEvjVuhsI1HciUBrepOGZet31fNCDDW8P oX+wUwY7aO9vBuigwgimgUP/rKThFLYxYAVKIiGShyp9evKm8iqS6ChI4jTiXqDaT7MQ ct3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680567242; 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=QYyKpmgAe3S55Nk5FWRs2dH0UIocesat7xjNxdFTU4k=; b=u1TvPNC/oiSDBdpCRgh+2Q3211+t+TjreY9GXKh6uke0d7FgTiHzsgyKNaen64MUQC i3CZrR3cquV11Oe6uAFMPxRrcmCmDnEEIY1EtzWs0hGHMEKRQqixQSzrs/IUIJGGG0aU eheQ0kNSO3F9ngV+Du9tSqM3kKsjZsBlCUif8f6JmS/agVPeoRfyPNlACt4/CqiygRE8 sCLR/nRbO5fR10OLKLllPeqjmOQgv8aj5iZ9fS+RXTyjXMV6N+eYg1wcnxbxnNsSjfGn UMzrU98Izv1f6QBW+UhuzWqUPVPADTNsOL3ST0Ldab/Pcrh8Hrw27j9zVINxiYmYavxD eChw== X-Gm-Message-State: AAQBX9e/LySkJ6uhVfEQJXiCF520kYmM2kDU62VAirvJeKjF7eqdFW7i O3iOunhXdj/uNwjOpN9LzOWgL42nAaNfdE6w X-Google-Smtp-Source: AKy350a8jpmup3Y0AoRXTeOyKKcgC2LVL+csu37K+C5/P3dMmovoTexr82+Hd4O52pTXV8PmQrABJAtIr5EvWJJc X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a05:6a00:2e14:b0:627:e6d5:ba2d with SMTP id fc20-20020a056a002e1400b00627e6d5ba2dmr223605pfb.6.1680567241767; Mon, 03 Apr 2023 17:14:01 -0700 (PDT) Date: Tue, 4 Apr 2023 00:13:53 +0000 In-Reply-To: <20230404001353.468224-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230404001353.468224-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230404001353.468224-4-yosryahmed@google.com> Subject: [PATCH v4 3/3] mm: vmscan: ignore non-LRU-based reclaim in memcg reclaim From: Yosry Ahmed To: Andrew Morton , 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 , Dave Chinner 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 simple way to currently 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. Writing to memory.reclaim on the root memcg is considered as cgroup_reclaim(), but for this case we want to include any freed pages, so use the global_reclaim() check instead. 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 | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 8f0e7c4e91ae3..049e39202e6ce 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -518,7 +518,35 @@ static void set_task_reclaim_state(struct task_struct *task, static void flush_reclaim_state(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 global 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 && global_reclaim(sc)) { sc->nr_reclaimed += rs->reclaimed; rs->reclaimed = 0; }