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 02222C433F5 for ; Wed, 9 Mar 2022 21:26:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229514AbiCIV11 (ORCPT ); Wed, 9 Mar 2022 16:27:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234910AbiCIV10 (ORCPT ); Wed, 9 Mar 2022 16:27:26 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A2C253711 for ; Wed, 9 Mar 2022 13:26:27 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9AC6E61AFE for ; Wed, 9 Mar 2022 21:26:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBFF0C340E8; Wed, 9 Mar 2022 21:26:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646861186; bh=sOkouGrGHWIOOOw9P8Yzd9RWhppCUaQbIRCHSKZW7Fs=; h=Date:To:From:Subject:From; b=CgG2GrP5JLAy6qBbECtQs6JU/WOSLUnq8fUviZAuNk8yBZdWruDNmrShgyaiHGnM4 2xfSCV9HUnw5s+0IMYxrmsGu4OWDRiQhvYssmxXd8Xwo6tNRupsYfUp9dRgQS3ufSL yTb0246TiKd3bzkwy9H2f9eyLwRlZ6a6cQm42Ppg= Date: Wed, 09 Mar 2022 13:26:25 -0800 To: mm-commits@vger.kernel.org, songmuchun@bytedance.com, shakeelb@google.com, roman.gushchin@linux.dev, mhocko@suse.com, hannes@cmpxchg.org, longman@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-list_lru-optimize-memcg_reparent_list_lru_node.patch added to -mm tree Message-Id: <20220309212625.EBFF0C340E8@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/list_lru: optimize memcg_reparent_list_lru_node() has been added to the -mm tree. Its filename is mm-list_lru-optimize-memcg_reparent_list_lru_node.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-list_lru-optimize-memcg_reparent_list_lru_node.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-list_lru-optimize-memcg_reparent_list_lru_node.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Waiman Long Subject: mm/list_lru: optimize memcg_reparent_list_lru_node() Since commit 2c80cd57c743 ("mm/list_lru.c: fix list_lru_count_node() to be race free"), we are tracking the total number of lru entries in a list_lru_node in its nr_items field. In the case of memcg_reparent_list_lru_node(), there is nothing to be done if nr_items is 0. We don't even need to take the nlru->lock as no new lru entry could be added by a racing list_lru_add() to the draining src_idx memcg at this point. On systems that serve a lot of containers, it is possible that there can be thousands of list_lru's present due to the fact that each container may mount its own container specific filesystems. As a typical container uses only a few cpus, it is likely that only the list_lru_node that contains those cpus will be utilized while the rests may be empty. In other words, there can be a lot of list_lru_node with 0 nr_items. By skipping a lock/unlock operation and loading a cacheline from memcg_lrus, a sizeable number of cpu cycles can be saved. That can be substantial if we are talking about thousands of list_lru_node's with 0 nr_items. Link: https://lkml.kernel.org/r/20220309144000.1470138-1-longman@redhat.com Signed-off-by: Waiman Long Reviewed-by: Roman Gushchin Cc: Muchun Song Cc: Michal Hocko Cc: Johannes Weiner Cc: Shakeel Butt Signed-off-by: Andrew Morton --- mm/list_lru.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/mm/list_lru.c~mm-list_lru-optimize-memcg_reparent_list_lru_node +++ a/mm/list_lru.c @@ -519,6 +519,12 @@ static void memcg_drain_list_lru_node(st struct list_lru_one *src, *dst; /* + * If there is no lru entry in this nlru, we can skip it immediately. + */ + if (!READ_ONCE(nlru->nr_items)) + return; + + /* * Since list_lru_{add,del} may be called under an IRQ-safe lock, * we have to use IRQ-safe primitives here to avoid deadlock. */ _ Patches currently in -mm which might be from longman@redhat.com are mm-list_lru-optimize-memcg_reparent_list_lru_node.patch lib-vsprintf-avoid-redundant-work-with-0-size.patch mm-page_owner-use-scnprintf-to-avoid-excessive-buffer-overrun-check.patch mm-page_owner-print-memcg-information.patch mm-page_owner-record-task-command-name.patch ipc-mqueue-use-get_tree_nodev-in-mqueue_get_tree.patch