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=-17.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 11F5DC433E0 for ; Mon, 8 Mar 2021 14:54:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8F5ED651B9 for ; Mon, 8 Mar 2021 14:54:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F5ED651B9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CC7468D0030; Mon, 8 Mar 2021 09:54:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C513D8D001D; Mon, 8 Mar 2021 09:54:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AF2038D0030; Mon, 8 Mar 2021 09:54:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id 901978D001D for ; Mon, 8 Mar 2021 09:54:46 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 5002B4DC1 for ; Mon, 8 Mar 2021 14:54:46 +0000 (UTC) X-FDA: 77897003772.16.AF9F87A Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf26.hostedemail.com (Postfix) with ESMTP id CD25E4080F54 for ; Mon, 8 Mar 2021 14:54:43 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id D45BA650E6; Mon, 8 Mar 2021 14:54:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615215284; bh=X0lo3Qat103XhQ7n/pn8ZYoJZykAVsMGsMiUCcu70Gg=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=spN/4KqC5tfWitVZ0K4hQKMgdT5PR7dE0yZ4vY3o/eTBu+ZJKHDmjX0GRAjR56shy sIBrrKwmWso/Ujqm3NAFRWP+nMmivkGG+eTEaF+1qPy62alkQ281yTtyuaE2EZauCs tWtbEHqaDqapcSrOg0sJ9PshTRbx7bGKEiAV1bwTvO/w0mPFLyZ00S6o6Gqg78SUBL URzO0Fblz7kem2JXTK+9UHraUjl+yXtrT3PxudL2JE9SMAP01qJ9UmTc97H6LNhdD/ 4yFZkn2E6Q4SttLFGWFWtbonCNKjX2Pp1YIXufEG0eOy3EObsGcLTgKM2IEGPq3yq2 YeYAJirKmLHMg== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 9C23B35239E1; Mon, 8 Mar 2021 06:54:44 -0800 (PST) Date: Mon, 8 Mar 2021 06:54:44 -0800 From: "Paul E. McKenney" To: Shakeel Butt Cc: Yang Shi , Roman Gushchin , Kirill Tkhai , Vlastimil Babka , Dave Chinner , Johannes Weiner , Michal Hocko , Andrew Morton , Linux MM , linux-fsdevel , LKML Subject: Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu Message-ID: <20210308145444.GN2696@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20210217001322.2226796-1-shy828301@gmail.com> <20210217001322.2226796-6-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Stat-Signature: idkjyommrcxoeazt5yfxotfxgbspc3ad X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CD25E4080F54 Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf26; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615215283-585873 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote: > On Tue, Feb 16, 2021 at 4:13 PM Yang Shi wrote: > > > > Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu(). > > We don't have to define a dedicated callback for call_rcu() anymore. > > > > Signed-off-by: Yang Shi > > --- > > mm/vmscan.c | 7 +------ > > 1 file changed, 1 insertion(+), 6 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 2e753c2516fa..c2a309acd86b 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items) > > return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long)); > > } > > > > -static void free_shrinker_map_rcu(struct rcu_head *head) > > -{ > > - kvfree(container_of(head, struct memcg_shrinker_map, rcu)); > > -} > > - > > static int expand_one_shrinker_map(struct mem_cgroup *memcg, > > int size, int old_size) > > { > > @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg, > > memset((void *)new->map + old_size, 0, size - old_size); > > > > rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new); > > - call_rcu(&old->rcu, free_shrinker_map_rcu); > > + kvfree_rcu(old); > > Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single > param can call synchronize_rcu(). Especially given that you already have the ->rcu field that the two-argument form requires. The reason for using the single-argument form is when you have lots of little data structures, such that getting rid of that rcu_head structure is valuable enough to be worth the occasional call to synchronize_rcu(). However, please note that this call to synchronize_rcu() happens only under OOM conditions. Thanx, Paul