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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 F0E34C433E2 for ; Mon, 22 Mar 2021 09:42:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C37696197F for ; Mon, 22 Mar 2021 09:42:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230173AbhCVJl5 (ORCPT ); Mon, 22 Mar 2021 05:41:57 -0400 Received: from mx2.suse.de ([195.135.220.15]:42326 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229647AbhCVJlt (ORCPT ); Mon, 22 Mar 2021 05:41:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1616406107; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2MrLrWusuMoiI8O7+3wbzgaIdF+kB6mkdoYQZJejkd4=; b=E8D+jDAB+COFZKQcu1xIYYrlMjFnpzSSEQuIxnyvEKfQx0biUZEIj+nLhEn2vmvJUbQNmH K3bE7QPucLJ9hKYrmqtXLCNBJRqkWS8KyFJRMX4AAB0BBVw0pYsDBd/0peRXIdpft3Zkrh mSDjAXUSYypyfpU/g4bLolctjgMumgk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B9D5AAD38; Mon, 22 Mar 2021 09:41:47 +0000 (UTC) Date: Mon, 22 Mar 2021 10:41:47 +0100 From: Michal Hocko To: Johannes Weiner Cc: Andrew Morton , Hugh Dickins , Shakeel Butt , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 1/2] mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled Message-ID: References: <20210319054944.50048-1-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210319054944.50048-1-hannes@cmpxchg.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 19-03-21 01:49:43, Johannes Weiner wrote: > Since commit 2d1c498072de ("mm: memcontrol: make swap tracking an > integral part of memory control"), the cgroup swap arrays are used to > track memory ownership at the time of swap readahead and swapoff, even > if swap space *accounting* has been turned off by the user via > swapaccount=0 (which sets cgroup_memory_noswap). > > However, the patch was overzealous: by simply dropping the > cgroup_memory_noswap conditionals in the swapon, swapoff and uncharge > path, it caused the cgroup arrays being allocated even when the memory > controller as a whole is disabled. This is a waste of that memory. > > Restore mem_cgroup_disabled() checks, implied previously by > cgroup_memory_noswap, in the swapon, swapoff, and swap_entry_free > callbacks. > > Fixes: 2d1c498072de ("mm: memcontrol: make swap tracking an integral part of memory control") > Reported-by: Hugh Dickins > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko > --- > mm/memcontrol.c | 3 +++ > mm/swap_cgroup.c | 6 ++++++ > 2 files changed, 9 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 668d1d7c2645..49bdcf603af1 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -7101,6 +7101,9 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages) > struct mem_cgroup *memcg; > unsigned short id; > > + if (mem_cgroup_disabled()) > + return; > + > id = swap_cgroup_record(entry, 0, nr_pages); > rcu_read_lock(); > memcg = mem_cgroup_from_id(id); > diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c > index 7f34343c075a..08c3246f9269 100644 > --- a/mm/swap_cgroup.c > +++ b/mm/swap_cgroup.c > @@ -171,6 +171,9 @@ int swap_cgroup_swapon(int type, unsigned long max_pages) > unsigned long length; > struct swap_cgroup_ctrl *ctrl; > > + if (mem_cgroup_disabled()) > + return 0; > + > length = DIV_ROUND_UP(max_pages, SC_PER_PAGE); > array_size = length * sizeof(void *); > > @@ -206,6 +209,9 @@ void swap_cgroup_swapoff(int type) > unsigned long i, length; > struct swap_cgroup_ctrl *ctrl; > > + if (mem_cgroup_disabled()) > + return; > + > mutex_lock(&swap_cgroup_mutex); > ctrl = &swap_cgroup_ctrl[type]; > map = ctrl->map; > -- > 2.30.1 > -- Michal Hocko SUSE Labs