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 X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30E49C2BC11 for ; Mon, 14 Sep 2020 14:59:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CAB6B21655 for ; Mon, 14 Sep 2020 14:59:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bgr9QGac" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726774AbgINO73 (ORCPT ); Mon, 14 Sep 2020 10:59:29 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:41793 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726864AbgINO64 (ORCPT ); Mon, 14 Sep 2020 10:58:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600095531; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p4EylP6DiiMU0xDyOAgmGkadg42XWec7eelWwk0KDc0=; b=bgr9QGacO+rrT8VwtKAUTbJ/z4GDHTDFdxMq62qBPJIcOt+deZ1Xwi960jmvG+K1dYXGjI beoZ11jQOQxEQTmiK/M8uKzgCpffDYUDN5vQMk84BpuXytKTCiICsv7tNcqc7uvwTK7rOq wUeQDJ9dmB2thGFCU+e4ZwMCtOGQzSU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-132-kbpRmOvBMeOFddDEB9xAAg-1; Mon, 14 Sep 2020 10:58:49 -0400 X-MC-Unique: kbpRmOvBMeOFddDEB9xAAg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3A848189E62E; Mon, 14 Sep 2020 14:58:47 +0000 (UTC) Received: from llong.remote.csb (ovpn-118-85.rdu2.redhat.com [10.10.118.85]) by smtp.corp.redhat.com (Postfix) with ESMTP id AF18C5DA60; Mon, 14 Sep 2020 14:58:45 +0000 (UTC) Subject: Re: [PATCH v3 2/3] mm/memcg: Simplify mem_cgroup_get_max() To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tejun Heo , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt , Chris Down , Roman Gushchin , Yafang Shao References: <20200914024452.19167-1-longman@redhat.com> <20200914141955.2145-1-longman@redhat.com> <20200914144739.GV16999@dhcp22.suse.cz> From: Waiman Long Organization: Red Hat Message-ID: <24d1cfe4-845e-0944-4187-217d345d59a5@redhat.com> Date: Mon, 14 Sep 2020 10:58:45 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200914144739.GV16999@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/14/20 10:47 AM, Michal Hocko wrote: > On Mon 14-09-20 10:19:55, Waiman Long wrote: >> The mem_cgroup_get_max() function used to get memory+swap max from >> both the v1 memsw and v2 memory+swap page counters & return the maximum >> of these 2 values. This is redundant and it is more efficient to just >> get either the v1 or the v2 values depending on which one is currently >> in use. >> >> Signed-off-by: Waiman Long >> --- >> mm/memcontrol.c | 24 +++++++++++++----------- >> 1 file changed, 13 insertions(+), 11 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 8c74f1200261..2331d4bc7c4d 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1633,17 +1633,19 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) >> */ >> unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg) >> { >> - unsigned long max; >> - >> - max = READ_ONCE(memcg->memory.max); >> - if (mem_cgroup_swappiness(memcg)) { >> - unsigned long memsw_max; >> - unsigned long swap_max; >> - >> - memsw_max = memcg->memsw.max; >> - swap_max = READ_ONCE(memcg->swap.max); >> - swap_max = min(swap_max, (unsigned long)total_swap_pages); >> - max = min(max + swap_max, memsw_max); >> + unsigned long max = READ_ONCE(memcg->memory.max); >> + >> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { >> + if (mem_cgroup_swappiness(memcg)) >> + max += min(READ_ONCE(memcg->swap.max), >> + (unsigned long)total_swap_pages); >> + } else { /* v1 */ >> + if (mem_cgroup_swappiness(memcg)) { >> + unsigned long memsw = READ_ONCE(memcg->memsw.max); >> + >> + if (memsw > max) >> + max += min(memsw - max, (unsigned long)total_swap_pages); > Yes this looks better. But, memsw can never be smaller than the hard > limit (mem_cgroup_resize_max). I would find it slightly easier to > understand if you did > /* calculate swap excess capacity from memsw limit*/ > unsigned long memsw = READ_ONCE(memcg->memsw.max) - max; > max += min (memsw, total_swap_pages); Right, I thought it was possible to set memsw lower than mem. It was not allowed. So the extra check is unnecessary. Will fix that. Cheers, Longman