From nobody Sun Feb 8 05:58:53 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 A1C0CE8180A for ; Fri, 22 Sep 2023 19:36:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232248AbjIVTgb (ORCPT ); Fri, 22 Sep 2023 15:36:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233426AbjIVR7e (ORCPT ); Fri, 22 Sep 2023 13:59:34 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 326C04211 for ; Fri, 22 Sep 2023 10:57:46 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d81a76a11eeso3071368276.3 for ; Fri, 22 Sep 2023 10:57:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695405465; x=1696010265; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=CIUVdWYJzS23SUkOVUGYlHJuolUCd+SBS6YJzjY/W/M=; b=j6jMO0KPP+GHBicZNd3LVMZSQuXiS/dwN9sDBeANBHBoOrl6GWQqcBMeYr+OhfGW41 j9DARkjCnZgGSkLQcbz2WN6qW1frdj3oCH4ytTmmXC3yQ8QLuYd6ANgEmbPFi+ZMhO/2 QojDnZ+NojRvcRFAVk5DLP+aIbCt2o5iCNj+r2udzeGho/0Wr1Bf7yD1ZIAh9zeJ/5+Y bnXcN+PNpLvDvIiP7kQBWTmMys97Lr5W7o9XlZIm4rjFchkQTs6S3Qeg9Cx8z0DR7W+c rx1b+qrC/O01Wcwk4hBmmEuUoSD+GtApnNOU1FGwwpi99VqjIcj+/LOmi44D5yZJultX NfOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695405465; x=1696010265; 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=CIUVdWYJzS23SUkOVUGYlHJuolUCd+SBS6YJzjY/W/M=; b=iKDFFQsOPKlg6WnUBMf94UsKFs/BkVdwDojLnr2CJSxFp0HUsOgF2+H0K26+La8R44 D+59NRt99cRZNn1ptePJ2AB5vrCfjaCEOt0Nid7McoSQjWKuCiVA5nIsAnnqHhp30jct i8yLfMwRp+jMeI6FssEw8v77ItN9ls8YALe0oUWnDEXwRg1OEx8D/YLlwOcqe5Ofn1bg qRkBX75N9+Sngi3DRswItZVgCOhpYVR2Q1ku/TZ3p1X/8pCml2sV7V787uiFHi2Qpa0V JZYWZDmWmtbbdtGTXYioT9qn8l+jdZp14naNQCNEsE02tGtg8L2q/d7Q0WyJuSWNLa4G 3fww== X-Gm-Message-State: AOJu0YyOeVueKE26nYYJqgB4Ci0+1uql1mNtxyg2tdOwwVR0B4eklVZQ wEBTvcV5aXkvTjNQ40pr6/uCPp2qtBxafoyg X-Google-Smtp-Source: AGHT+IGRY7CHNarSt8hxzLUxdPvhzPSOwb+6g2+4WOANIpjP9cYGG1L1f1r5GlTbEtZccPZQJPzwzGGJFWlsxbc8 X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:29b4]) (user=yosryahmed job=sendgmr) by 2002:a25:6942:0:b0:d80:cf4:7e80 with SMTP id e63-20020a256942000000b00d800cf47e80mr453ybc.7.1695405465321; Fri, 22 Sep 2023 10:57:45 -0700 (PDT) Date: Fri, 22 Sep 2023 17:57:39 +0000 In-Reply-To: <20230922175741.635002-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230922175741.635002-1-yosryahmed@google.com> X-Mailer: git-send-email 2.42.0.515.g380fc7ccd1-goog Message-ID: <20230922175741.635002-2-yosryahmed@google.com> Subject: [PATCH v2 1/2] mm: memcg: refactor page state unit helpers From: Yosry Ahmed To: Andrew Morton , Shakeel Butt Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" memcg_page_state_unit() is currently used to identify the unit of a memcg state item so that all stats in memory.stat are in bytes. However, it lies about the units of WORKINGSET_* stats. These stats actually represent pages, but we present them to userspace as a scalar number of events. In retrospect, maybe those stats should have been memcg "events" rather than memcg "state". In preparation for using memcg_page_state_unit() for other purposes that need to know the truthful units of different stat items, break it down into two helpers: - memcg_page_state_unit() retuns the actual unit of the item. - memcg_page_state_output_unit() returns the unit used for output. Use the latter instead of the former in memcg_page_state_output() and lruvec_page_state_output(). While we are at it, let's show cgroup v1 some love and add memcg_page_state_local_output() for consistency. No functional change intended. Signed-off-by: Yosry Ahmed Acked-by: Johannes Weiner --- mm/memcontrol.c | 44 +++++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 927c64d3cbcb..308cc7353ef0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1535,7 +1535,7 @@ static const struct memory_stat memory_stats[] =3D { { "workingset_nodereclaim", WORKINGSET_NODERECLAIM }, }; =20 -/* Translate stat items to the correct unit for memory.stat output */ +/* The actual unit of the state item, not the same as the output unit */ static int memcg_page_state_unit(int item) { switch (item) { @@ -1543,6 +1543,22 @@ static int memcg_page_state_unit(int item) case MEMCG_ZSWAP_B: case NR_SLAB_RECLAIMABLE_B: case NR_SLAB_UNRECLAIMABLE_B: + return 1; + case NR_KERNEL_STACK_KB: + return SZ_1K; + default: + return PAGE_SIZE; + } +} + +/* Translate stat items to the correct unit for memory.stat output */ +static int memcg_page_state_output_unit(int item) +{ + /* + * Workingset state is actually in pages, but we export it to userspace + * as a scalar count of events, so special case it here. + */ + switch (item) { case WORKINGSET_REFAULT_ANON: case WORKINGSET_REFAULT_FILE: case WORKINGSET_ACTIVATE_ANON: @@ -1551,17 +1567,23 @@ static int memcg_page_state_unit(int item) case WORKINGSET_RESTORE_FILE: case WORKINGSET_NODERECLAIM: return 1; - case NR_KERNEL_STACK_KB: - return SZ_1K; default: - return PAGE_SIZE; + return memcg_page_state_unit(item); } } =20 static inline unsigned long memcg_page_state_output(struct mem_cgroup *mem= cg, int item) { - return memcg_page_state(memcg, item) * memcg_page_state_unit(item); + return memcg_page_state(memcg, item) * + memcg_page_state_output_unit(item); +} + +static inline unsigned long memcg_page_state_local_output( + struct mem_cgroup *memcg, int item) +{ + return memcg_page_state_local(memcg, item) * + memcg_page_state_output_unit(item); } =20 static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) @@ -4106,9 +4128,8 @@ static void memcg1_stat_format(struct mem_cgroup *mem= cg, struct seq_buf *s) for (i =3D 0; i < ARRAY_SIZE(memcg1_stats); i++) { unsigned long nr; =20 - nr =3D memcg_page_state_local(memcg, memcg1_stats[i]); - seq_buf_printf(s, "%s %lu\n", memcg1_stat_names[i], - nr * memcg_page_state_unit(memcg1_stats[i])); + nr =3D memcg_page_state_local_output(memcg, memcg1_stats[i]); + seq_buf_printf(s, "%s %lu\n", memcg1_stat_names[i], nr); } =20 for (i =3D 0; i < ARRAY_SIZE(memcg1_events); i++) @@ -4134,9 +4155,9 @@ static void memcg1_stat_format(struct mem_cgroup *mem= cg, struct seq_buf *s) for (i =3D 0; i < ARRAY_SIZE(memcg1_stats); i++) { unsigned long nr; =20 - nr =3D memcg_page_state(memcg, memcg1_stats[i]); + nr =3D memcg_page_state_output(memcg, memcg1_stats[i]); seq_buf_printf(s, "total_%s %llu\n", memcg1_stat_names[i], - (u64)nr * memcg_page_state_unit(memcg1_stats[i])); + (u64)nr); } =20 for (i =3D 0; i < ARRAY_SIZE(memcg1_events); i++) @@ -6614,7 +6635,8 @@ static int memory_stat_show(struct seq_file *m, void = *v) static inline unsigned long lruvec_page_state_output(struct lruvec *lruvec, int item) { - return lruvec_page_state(lruvec, item) * memcg_page_state_unit(item); + return lruvec_page_state(lruvec, item) * + memcg_page_state_output_unit(item); } =20 static int memory_numa_stat_show(struct seq_file *m, void *v) --=20 2.42.0.515.g380fc7ccd1-goog From nobody Sun Feb 8 05:58:53 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 32821CD4847 for ; Fri, 22 Sep 2023 18:05:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233059AbjIVSFS (ORCPT ); Fri, 22 Sep 2023 14:05:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233538AbjIVSFJ (ORCPT ); Fri, 22 Sep 2023 14:05:09 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A1664223 for ; Fri, 22 Sep 2023 10:57:48 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d81d85aae7cso437482276.0 for ; Fri, 22 Sep 2023 10:57:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695405467; x=1696010267; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=3CSLPc6OXSIH75VPEK2Or6+ByoA8DGo3BCTW1zZyxTA=; b=XSDFVFUj0s4Agwlv19dfVnA8fyANS3Lio1Mu22DmB1ClvVA1YT+CSVeqE0EWxIbDkm SAOwHueWm2RAHr7SLAyT7mtrmUF/p3ORh/dRzumeM8ShBlB/eZ49uVQkTDrPZvOXa3XG U29dF0ipmdT7qgaXW/sTeHjT5QcTJTbW0lQMSCXZoeo/RTkaUTIwfORnOtEzIRVTLqd8 bXAbpQVdO5Lhp7LQ1XxgAJ4MTH98wJEJ9XVqEtqyOKGB7vCX6eCUAODfsLHNMKALhOHf 9vlWXS0Zt6co266BHa3btRr3isBFVGn1eqvxEeXTsc7qG3q58Ws3hXBi5lb3+lId+t+K Pq+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695405467; x=1696010267; 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=3CSLPc6OXSIH75VPEK2Or6+ByoA8DGo3BCTW1zZyxTA=; b=IwnWH1DYAPMya73C4veAFt0ga+a0hCiDNIhEvPpvZ1Efq6f0fonuf+GxaX/7TtbBuj mI8F/oLTbrg9io/KaFONYzsYlQKO6N3eMLASZ4fPTHQGoDgM4tdfJJfIBzmSwcaWPIa4 nKPuHdsKmzV4hYYTigeVGFp9JEP1pVPD9I8Gq67bCCmPxufc78XPirUNQ+sauYaAVVoX N3RB0qVeLqptt9sAPTeL9wCKsc2mT4CjuBSdO96yNfkncocogB0fbX3BJZrTleurn1F1 jp+0IwJkBAXzTo1oxbl/kwGAlWMYnnQ0VZHGLOKyoBLx6AT3tGfryctVFh23DPK+4rP6 qO9A== X-Gm-Message-State: AOJu0YzF5JLAoqQhYrXuXmTbM5xhR3ncYfBz515OwLn6cdp8PCKzaetL lq7jfdg/MudyZLK5aVQyWRMY3Sw4lcdJk/0f X-Google-Smtp-Source: AGHT+IH/GVgcWoyTnI6CjuidQQj2eCHCb/7OcETmpcRHx+mMydVisjSv3mlfwbIqt/FcEH+WIvuFEmX/eSnvqJcR X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:29b4]) (user=yosryahmed job=sendgmr) by 2002:a25:8304:0:b0:d86:5913:55cb with SMTP id s4-20020a258304000000b00d86591355cbmr1694ybk.0.1695405467283; Fri, 22 Sep 2023 10:57:47 -0700 (PDT) Date: Fri, 22 Sep 2023 17:57:40 +0000 In-Reply-To: <20230922175741.635002-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230922175741.635002-1-yosryahmed@google.com> X-Mailer: git-send-email 2.42.0.515.g380fc7ccd1-goog Message-ID: <20230922175741.635002-3-yosryahmed@google.com> Subject: [PATCH v2 2/2] mm: memcg: normalize the value passed into memcg_rstat_updated() From: Yosry Ahmed To: Andrew Morton , Shakeel Butt Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" memcg_rstat_updated() uses the value of the state update to keep track of the magnitude of pending updates, so that we only do a stats flush when it's worth the work. Most values passed into memcg_rstat_updated() are in pages, however, a few of them are actually in bytes or KBs. To put this into perspective, a 512 byte slab allocation today would look the same as allocating 512 pages. This may result in premature flushes, which means unnecessary work and latency. Normalize all the state values passed into memcg_rstat_updated() to pages. Round up non-zero sub-page to 1 page, because memcg_rstat_updated() ignores 0 page updates. Fixes: 5b3be698a872 ("memcg: better bounds on the memcg stats updates") Signed-off-by: Yosry Ahmed Acked-by: Johannes Weiner --- mm/memcontrol.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 308cc7353ef0..d1a322a75172 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -763,6 +763,22 @@ unsigned long memcg_page_state(struct mem_cgroup *memc= g, int idx) return x; } =20 +static int memcg_page_state_unit(int item); + +/* + * Normalize the value passed into memcg_rstat_updated() to be in pages. R= ound + * up non-zero sub-page updates to 1 page as zero page updates are ignored. + */ +static int memcg_state_val_in_pages(int idx, int val) +{ + int unit =3D memcg_page_state_unit(idx); + + if (!val || unit =3D=3D PAGE_SIZE) + return val; + else + return max(val * unit / PAGE_SIZE, 1UL); +} + /** * __mod_memcg_state - update cgroup memory statistics * @memcg: the memory cgroup @@ -775,7 +791,7 @@ void __mod_memcg_state(struct mem_cgroup *memcg, int id= x, int val) return; =20 __this_cpu_add(memcg->vmstats_percpu->state[idx], val); - memcg_rstat_updated(memcg, val); + memcg_rstat_updated(memcg, memcg_state_val_in_pages(idx, val)); } =20 /* idx can be of type enum memcg_stat_item or node_stat_item. */ @@ -826,7 +842,7 @@ void __mod_memcg_lruvec_state(struct lruvec *lruvec, en= um node_stat_item idx, /* Update lruvec */ __this_cpu_add(pn->lruvec_stats_percpu->state[idx], val); =20 - memcg_rstat_updated(memcg, val); + memcg_rstat_updated(memcg, memcg_state_val_in_pages(idx, val)); memcg_stats_unlock(); } =20 --=20 2.42.0.515.g380fc7ccd1-goog