From mboxrd@z Thu Jan 1 00:00:00 1970 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 C5F46C761AF for ; Mon, 3 Apr 2023 22:04:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233746AbjDCWEJ (ORCPT ); Mon, 3 Apr 2023 18:04:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233615AbjDCWDq (ORCPT ); Mon, 3 Apr 2023 18:03:46 -0400 Received: from mail-pg1-x549.google.com (mail-pg1-x549.google.com [IPv6:2607:f8b0:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F98335A9 for ; Mon, 3 Apr 2023 15:03:45 -0700 (PDT) Received: by mail-pg1-x549.google.com with SMTP id q15-20020a63d60f000000b00502e1c551aaso9005648pgg.21 for ; Mon, 03 Apr 2023 15:03:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680559424; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=kF9j9xhVt+HAtgUv/sW6MmUPAVRA6NHiHn3mXAJRGAA=; b=QZZrc3A9Ala3Y1fUrUeH9aHQEpEHIm56zSkCNE0A0d2CfnkVvyEn83miymwgAbVi5v 9d0zVCVjgbHefP1pXO+Nwo1Ul1PtmNl2tpG2LpPChio/My4WZElf1o1jchSNOgvJZUsW WbV5lrmHTcH3fAqoJ7gZenJSRA3/dWbn3kNYUTeryGOWXdDf83/N+i1IFVKcpHglHDCj nH4nWeMmhgItD/X0NlX5brqxxgrkgNj//KowEl9SOf+dOa58iks3E9glke7V87blHVFo T2x7kiC5rzRzeUUzMZ/tXlij1MqA5Wi+XXZnHplS+57XrL+yaVLwig14jPX/om3gIc+M IAag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680559424; 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=kF9j9xhVt+HAtgUv/sW6MmUPAVRA6NHiHn3mXAJRGAA=; b=JWtFcwwgI+rnKFHkD62RC2ZavEcq8ZhXWDt1rurNg+y/TRMCamP0Ul4ynSVoKNeYxH V9GXqDDPOByl2i8oX2jEbxYmCwspIysZ0gco+3/JPzbhpXYTF4WKrXGfkuSkPF2uViMD PR5rSDe2cbXTnbzzHrDF6LMYlseJ1BVODucr7ZRGew5pFmpNdvuG3mklHcT3DREn/PSj FWvVC3CF/5s214gvK8N0q3xDGvL5bOyUuCmr8p5QNhADzm0O2Z0+QOVF3oJcHNZHWv/Y ya+KrVxzB9PWl43FXJGHBd2+bHfHtZGurc+oEmxsJzC0ic/Zwi0NGiJvaBeqN4sPxNoY ahzA== X-Gm-Message-State: AAQBX9c2lZVG1AxG/1UwsoFp0b2MOXK8VaZxl7NoAiBnHrImdrOpxspx 5l4JsDnb3vJkqEz/SI1H8p9ukScwQlz6B/yy X-Google-Smtp-Source: AKy350Y61C08ugQDQ0T+NdoZquMxt4ZL2sOiJByhoRsOjzxwb2aWtKxGtikw0lJtgE93Bg+tt+KjbLE8KoMgZHnh X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a63:2301:0:b0:503:91ff:8dd8 with SMTP id j1-20020a632301000000b0050391ff8dd8mr27700pgj.4.1680559424700; Mon, 03 Apr 2023 15:03:44 -0700 (PDT) Date: Mon, 3 Apr 2023 22:03:35 +0000 In-Reply-To: <20230403220337.443510-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230403220337.443510-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230403220337.443510-4-yosryahmed@google.com> Subject: [PATCH mm-unstable RFC 3/5] memcg: calculate root usage from global state From: Yosry Ahmed To: Alexander Viro , Christian Brauner , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Yosry Ahmed Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, we approximate the root usage by adding the memcg stats for anon, file, and conditionally swap (for memsw). To read the memcg stats we need to invoke an rstat flush. rstat flushes can be expensive, they scale with the number of cpus and cgroups on the system. mem_cgroup_usage() is called by memcg_events()->mem_cgroup_threshold() with irqs disabled, so such an expensive operation with irqs disabled can cause problems. Instead, approximate the root usage from global state. This is not 100% accurate, but the root usage has always been ill-defined anyway. Signed-off-by: Yosry Ahmed --- mm/memcontrol.c | 24 +++++------------------- 1 file changed, 5 insertions(+), 19 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index bdd52fe9e7e4b..e7fe18c0c0ef2 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3698,27 +3698,13 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) if (mem_cgroup_is_root(memcg)) { /* - * We can reach here from irq context through: - * uncharge_batch() - * |--memcg_check_events() - * |--mem_cgroup_threshold() - * |--__mem_cgroup_threshold() - * |--mem_cgroup_usage - * - * rstat flushing is an expensive operation that should not be - * done from irq context; use stale stats in this case. - * Arguably, usage threshold events are not reliable on the root - * memcg anyway since its usage is ill-defined. - * - * Additionally, other call paths through memcg_check_events() - * disable irqs, so make sure we are flushing stats atomically. + * Approximate root's usage from global state. This isn't + * perfect, but the root usage was always an approximation. */ - if (in_task()) - mem_cgroup_flush_stats_atomic(); - val = memcg_page_state(memcg, NR_FILE_PAGES) + - memcg_page_state(memcg, NR_ANON_MAPPED); + val = global_node_page_state(NR_FILE_PAGES) + + global_node_page_state(NR_ANON_MAPPED); if (swap) - val += memcg_page_state(memcg, MEMCG_SWAP); + val += total_swap_pages - get_nr_swap_pages(); } else { if (!swap) val = page_counter_read(&memcg->memory); -- 2.40.0.348.gf938b09366-goog