From nobody Wed Feb 11 09:38:45 2026 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 0A5B9C76188 for ; Wed, 5 Apr 2023 18:54:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233685AbjDESyk (ORCPT ); Wed, 5 Apr 2023 14:54:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234360AbjDESyd (ORCPT ); Wed, 5 Apr 2023 14:54:33 -0400 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 6659E3A9D for ; Wed, 5 Apr 2023 11:54:32 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-54be7584b28so48934337b3.16 for ; Wed, 05 Apr 2023 11:54:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680720871; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=oB2sMXwt0v6x8lwXtmYlxh/hoioeozIJIVJcuuQJKWA=; b=Ros0vevjUiwI3/TjUKg+KCeA5SHnfksHcC4OK3M0Fn4fXpXuUrynI6b8MaR9/c3jSk kYtK4Ske7kxweFphiQTIVIVAbS/Fuv7jZA8Wq1GWNo0oxzQ5Nh5pojz9jDp+do2ph3Jj IztRjzkxwy2vWa3oGo525fcM6H4ZEmqQU6p4rYHtfJsYsBqy2LUHEZvuMUuNIKTo/uqK Xwb0LLWXZaQYVo8lUIEKsrrCdSMMCxNVxpuQ+1xdxcKxOZL6ys2NO41rWyag1l5oLhzt LVX/O/QEV66s0ajoxgyOizIIfKMnIekWa445aOdc74s+Q8ItuYHAsLFXOFgFRUjGTZ12 4y1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680720871; 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=oB2sMXwt0v6x8lwXtmYlxh/hoioeozIJIVJcuuQJKWA=; b=rkpGbyMUQI5ryVu1+CEgXe9Y3vooOD8k9bRC7nh7y6hUEgYQ3KtG5Pb0gBZCUSXrX6 dYUGhyGsARBVRcMYRbHbDEu2OphPqFsoposK3FrBDToQbhieHjLvXc54TNEe07ZcM/QJ OEXpyCzGbraPiArHOh8IlRMqMMLYOF86htniQMSa+pQ6sWkKNRS02Yhptte3uImvMzoT pE+u4MSxGeNIqS6wA4W0pR8md2lpfv84vV9lUMOJqtWNSh5R+MhIxS7/cCy51NdjXNrv L/KI1ghiOeDLQI8BRWUNAo+RJbggvgqV2VV4gNJ7t0feAlSNfiERosFVazISvLPAvj7a sl7A== X-Gm-Message-State: AAQBX9eZGWji6aFhDDNhe14MDfi/6A5wu8kCWJHI268ObfWltrKcBiDX +JtArBsJ+VebVC2+bP1t7j9clkcEl9fcv0V1 X-Google-Smtp-Source: AKy350ZCAIete9IDtcJDwB8xbNQZBALRdtx0fEvZ0QLo3PyT+UesbYmBb8Uc0roxQG5ktSucSqhPRJ3viu7kH1ie X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a25:d986:0:b0:b8b:eea7:525c with SMTP id q128-20020a25d986000000b00b8beea7525cmr163875ybg.9.1680720871655; Wed, 05 Apr 2023 11:54:31 -0700 (PDT) Date: Wed, 5 Apr 2023 18:54:26 +0000 In-Reply-To: <20230405185427.1246289-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230405185427.1246289-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230405185427.1246289-2-yosryahmed@google.com> Subject: [PATCH v5 1/2] 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 , stable@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" We keep track of different types of reclaimed pages through reclaim_state->reclaimed_slab, 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 of !cgroup_reclaim(). 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. The next patch performs some cleanups around reclaim_state and adds an elaborate comment explaining this to the code. This patch is kept minimal for easy backporting. Signed-off-by: Yosry Ahmed Cc: stable@vger.kernel.org --- global_reclaim(sc) does not exist in kernels before 6.3. It can be replaced with: !cgroup_reclaim(sc) || mem_cgroup_is_root(sc->target_mem_cgroup) --- mm/vmscan.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 9c1c5e8b24b8f..c82bd89f90364 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5346,8 +5346,10 @@ static int shrink_one(struct lruvec *lruvec, struct = scan_control *sc) vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned, sc->nr_reclaimed - reclaimed); =20 - sc->nr_reclaimed +=3D current->reclaim_state->reclaimed_slab; - current->reclaim_state->reclaimed_slab =3D 0; + if (global_reclaim(sc)) { + sc->nr_reclaimed +=3D current->reclaim_state->reclaimed_slab; + current->reclaim_state->reclaimed_slab =3D 0; + } =20 return success ? MEMCG_LRU_YOUNG : 0; } @@ -6472,7 +6474,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan= _control *sc) =20 shrink_node_memcgs(pgdat, sc); =20 - if (reclaim_state) { + if (reclaim_state && global_reclaim(sc)) { sc->nr_reclaimed +=3D reclaim_state->reclaimed_slab; reclaim_state->reclaimed_slab =3D 0; } --=20 2.40.0.348.gf938b09366-goog