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=-12.7 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 E1D24C433DF for ; Thu, 20 Aug 2020 20:29:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE91B207DE for ; Thu, 20 Aug 2020 20:29:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UqoHrxDC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728381AbgHTU3i (ORCPT ); Thu, 20 Aug 2020 16:29:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:38971 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726908AbgHTU3h (ORCPT ); Thu, 20 Aug 2020 16:29:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597955375; 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=bqTEDMhBKHUNdE/xOyKTnipumO1ldzx6XH3nmOiyvQQ=; b=UqoHrxDCUmVGNuNcjX3y5BjoF2tgaUImBNGrCwRDViVBs1s+5iIBRSrF/O1JyDobx4q+jy mWDSWtxy/fxtSQQ5ceNPpEYMhtSphwX0pWk+VxmYfbJa1fQRChKqY6UEQmdBcveqGtVYVK MR5QQexJ+YsFvOghE+dWdSRs9Mg43Yo= 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-274-EUGSS4-LNaCluMQg0kLEHw-1; Thu, 20 Aug 2020 16:29:31 -0400 X-MC-Unique: EUGSS4-LNaCluMQg0kLEHw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B0CF364080; Thu, 20 Aug 2020 20:29:29 +0000 (UTC) Received: from llong.remote.csb (unknown [10.10.115.249]) by smtp.corp.redhat.com (Postfix) with ESMTP id AE10039A55; Thu, 20 Aug 2020 20:29:27 +0000 (UTC) Subject: Re: [PATCH 2/3] mm/memcg: Simplify mem_cgroup_get_max() To: Johannes Weiner Cc: Michal Hocko , 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: <20200820130350.3211-1-longman@redhat.com> <20200820130350.3211-3-longman@redhat.com> <20200820173546.GB912520@cmpxchg.org> From: Waiman Long Organization: Red Hat Message-ID: Date: Thu, 20 Aug 2020 16:29:27 -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: <20200820173546.GB912520@cmpxchg.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/20/20 1:35 PM, Johannes Weiner wrote: > On Thu, Aug 20, 2020 at 09:03:49AM -0400, 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 | 14 +++++--------- >> 1 file changed, 5 insertions(+), 9 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 26b7a48d3afb..d219dca5239f 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1633,17 +1633,13 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) >> */ >> unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg) >> { >> - unsigned long max; >> + unsigned long max = READ_ONCE(memcg->memory.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); >> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) >> + max += READ_ONCE(memcg->swap.max); >> + else >> + max = memcg->memsw.max; > I agree with the premise of the patch, but v1 and v2 have sufficiently > different logic, and the way v1 overrides max from the innermost > branch again also doesn't help in understanding what's going on. > > Can you please split out the v1 and v2 code? > > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { > max = READ_ONCE(memcg->memory.max); > if (mem_cgroup_swappiness(memcg)) > max += READ_ONCE(memcg->swap.max); > } else { > if (mem_cgroup_swappiness(memcg)) > max = memcg->memsw.max; > else > max = READ_ONCE(memcg->memory.max); > } > > It's slightly repetitive, but IMO much more readable. > Sure. That makes it even better. Cheers, Longman