From patchwork Tue Mar 28 06:16:32 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13190567 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 7F1DAC77B60 for ; Tue, 28 Mar 2023 06:17:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232543AbjC1GRL (ORCPT ); Tue, 28 Mar 2023 02:17:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232464AbjC1GRD (ORCPT ); Tue, 28 Mar 2023 02:17:03 -0400 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [IPv6:2607:f8b0:4864:20::1049]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D84253A85 for ; Mon, 27 Mar 2023 23:16:47 -0700 (PDT) Received: by mail-pj1-x1049.google.com with SMTP id b16-20020a17090a991000b0023f803081beso2939299pjp.3 for ; Mon, 27 Mar 2023 23:16:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1679984207; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=wILXj9LqWwom+6PQC1+rRSpOfUrkR+GzdkCDGSSBhGY=; b=sq4WxgrXs35T1kNaqttQxLQHBBfHPzw9iKcGHtZRmWn7KoDZlSxKdNufMOgLyKUFr+ TMiE/wqtjNlMTixUEQeY/Vrw6MeR14OOP90t7VeDCccykNrGNGWLRshNs7Tr5dzPpQxM EqNAZipGy1I27uXZW4pV5ZH3WWGxC9s0suXWrK0/Qi+Fx4TfEA0shsUjup5r4I0T4jcO otnYwmVT7RvIIuwqMJTULG/AsEi9P5/3lltCZIuxMi9242jZnrgGHko3vAN7pXgBxOSv 6bmFPpVjK2j81kXxaYSwcWty18LJNFnzIpVeFZG9+e6GZQd6MIhYJNlu+ckzRRvaCz8L Rlqg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679984207; 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=wILXj9LqWwom+6PQC1+rRSpOfUrkR+GzdkCDGSSBhGY=; b=SURsZkIetGXaZBRsXTvD5QXg4R6KZhZL+d5E0w4gN2bz5dvS7T+PNJyusNSjCvjgRv 7ASxyECIQYSPkcuJV5kLV+mDuijcQ5Fg2uoRRaIGWa3p/VYNk8H8FwCfvnX785Y1reM/ 2bQYZxPnxS4WAv65+wU8yYp1cK4AXk5UwcNIYDJ8z6BQhYJopfzsu8srGPSnlG/nL7eg dyw+8Xw1tm3VJBsCqOXSPvD1EOFfNX6FDiyx5U9Yyrd6/bU+6VpWvoiL3Dy0rdIgiYPi A6e4ogq58ePiMxdtduKsfM8wpzYUMXpjQm0R4WW8nBShtcIv4s8qbZ7R9pxpvdy0Kjdi AWGw== X-Gm-Message-State: AO0yUKU98ki+dbCYNbhxt1usDZ2+LKRAO2qmk14e+tASOyQ/G3e4gDaI rI7VpjFrKbvH81Oi/ZA21thSnfAEvKFj01L0 X-Google-Smtp-Source: AK7set/NXJ9x9Sdrim9yKl61I9Pd5pvCD8XFm/ZA+2N5HaWD82pwRjDqKXOdg8RZFiQsg1c0bhIGvLI1ByyxVbFu X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a05:6a00:4510:b0:626:1710:9b7d with SMTP id cw16-20020a056a00451000b0062617109b7dmr8924786pfb.0.1679984207461; Mon, 27 Mar 2023 23:16:47 -0700 (PDT) Date: Tue, 28 Mar 2023 06:16:32 +0000 In-Reply-To: <20230328061638.203420-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230328061638.203420-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230328061638.203420-4-yosryahmed@google.com> Subject: [PATCH v1 3/9] 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 Precedence: bulk List-ID: X-Mailing-List: linux-block@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 --- 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)