From patchwork Thu Mar 30 19:17:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13194747 X-Patchwork-Delegate: kuba@kernel.org 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 5FF90C77B60 for ; Thu, 30 Mar 2023 19:18:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232097AbjC3TSU (ORCPT ); Thu, 30 Mar 2023 15:18:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232068AbjC3TSN (ORCPT ); Thu, 30 Mar 2023 15:18:13 -0400 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 674D3FF16 for ; Thu, 30 Mar 2023 12:18:10 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-54574d6204aso197363467b3.15 for ; Thu, 30 Mar 2023 12:18:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680203889; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=aVus0GFA9nzxOZ5lNIH1Nx8kHcLEa/aLkX98gl9HKOI=; b=Rb2fsB8aWLuAh/6UfhLacuvSldBOfVahXww4db+vgAZH6d8hHK5iS/Pb3yBuHu8zXu 8OHs3K+JgNd5BWKL8HmUqSNmeBMWOUfM93BgScQIJGiFyUTuS/OhqqsgB8B/zESgECWW id0La031n/vRfUHiqMH5ptV4ZUHLtuC1awDopegwUjfP8gYPSzkD9GboR6Sv+BT5F0il 4cP0p/kpaTUv9ECKBi7X6nDyHboM9b8Z+lLZ6iyDmkLsMIt+cWstg1DQo4e/ZnrIN56I iRBi8QgWvfbGxJTMXxv2zZuY7CwzGwzqEOEYe4XvyV9MRzo4MibTgBPKLkzWKa272DY9 IgGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680203889; 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=aVus0GFA9nzxOZ5lNIH1Nx8kHcLEa/aLkX98gl9HKOI=; b=7XR/xUhcdZsWkNctqqCn4GX755dPHJHPnPglrZnNbEI+rXcONkgqCB4kv4weAdARIz Zc14mjIgolC8ZBxAeAQp08riVPeN7bFKS0KvEs+gkW10KpXKdwI1CdSQutvBtpLNPpV9 V5hxyEzgQMIspeF3wVCQ/yfjvFCa4SIhX2fsow4GwJkDvaZuxX+cvIQZpj8RiYABOtjn 2bNE4NiNqRBNeFGWLmWGxsqbgdrzy5U70TqmjZxj+daKMpeFbVl9jN57tmgC6qA8zPz6 /eAyxjGBm5x55fUeFlI1z+w4L1NxgNA3r329pBYuziQQKeLfidr0QCWHivcsiojAWZ5t ZYgA== X-Gm-Message-State: AAQBX9cHAm+Jf0S/hp/7OBRfNXFk/xSKIHzokpaiqUw1r7y8IcWbRoEa gda5dbUdXgv7kzv43M+rzFju9Ujpk+aIZS81 X-Google-Smtp-Source: AKy350az4CClmAfjDaxG6/AcT2u/aalMEwRTuNYj9qh25Mudi/3feszrufxHB4k9is1ESXC81UQXzGZVI+EC5ExV X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a05:6902:10c3:b0:b79:4826:e8e3 with SMTP id w3-20020a05690210c300b00b794826e8e3mr10930499ybu.1.1680203889210; Thu, 30 Mar 2023 12:18:09 -0700 (PDT) Date: Thu, 30 Mar 2023 19:17:56 +0000 In-Reply-To: <20230330191801.1967435-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230330191801.1967435-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230330191801.1967435-4-yosryahmed@google.com> Subject: [PATCH v3 3/8] memcg: do not flush stats in irq context From: Yosry Ahmed To: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , " =?utf-8?q?Michal_Koutn=C3=BD?= " Cc: Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Yosry Ahmed , Michal Hocko Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Currently, the only context in which we can invoke an rstat flush from irq context is through mem_cgroup_usage() on the root memcg when called from memcg_check_events(). An rstat flush is an expensive operation that should not be done in irq context, so do not flush stats and use the stale stats in this case. Arguably, usage threshold events are not reliable on the root memcg anyway since its usage is ill-defined. Suggested-by: Johannes Weiner Suggested-by: Shakeel Butt Signed-off-by: Yosry Ahmed Acked-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko --- mm/memcontrol.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c3b6aae78901..ff39f78f962e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3669,7 +3669,21 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) unsigned long val; if (mem_cgroup_is_root(memcg)) { - mem_cgroup_flush_stats(); + /* + * 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. + */ + if (in_task()) + mem_cgroup_flush_stats(); val = memcg_page_state(memcg, NR_FILE_PAGES) + memcg_page_state(memcg, NR_ANON_MAPPED); if (swap)