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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 18402C433E0 for ; Wed, 8 Jul 2020 11:35:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D9B602067D for ; Wed, 8 Jul 2020 11:35:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9B602067D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6F9516B00F3; Wed, 8 Jul 2020 07:35:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6AA586B00F5; Wed, 8 Jul 2020 07:35:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5C0476B00F6; Wed, 8 Jul 2020 07:35:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0108.hostedemail.com [216.40.44.108]) by kanga.kvack.org (Postfix) with ESMTP id 474766B00F3 for ; Wed, 8 Jul 2020 07:35:12 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C5CB7DDEC for ; Wed, 8 Jul 2020 11:35:11 +0000 (UTC) X-FDA: 77014702422.15.meal66_120016726ebc Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id A9610181C43CB for ; Wed, 8 Jul 2020 11:17:11 +0000 (UTC) X-HE-Tag: meal66_120016726ebc X-Filterd-Recvd-Size: 2577 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Wed, 8 Jul 2020 11:17:11 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 513BBAD5C; Wed, 8 Jul 2020 11:17:10 +0000 (UTC) Subject: Re: [PATCH 3/3] mm: kmem: switch to static_branch_likely() in memcg_kmem_enabled() To: Roman Gushchin , Andrew Morton Cc: Johannes Weiner , Michal Hocko , Shakeel Butt , linux-mm@kvack.org, kernel-team@fb.com, linux-kernel@vger.kernel.org References: <20200707173612.124425-1-guro@fb.com> <20200707173612.124425-3-guro@fb.com> From: Vlastimil Babka Message-ID: <302e96c9-01ba-cdf3-1f50-8d33572d6ba4@suse.cz> Date: Wed, 8 Jul 2020 13:17:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200707173612.124425-3-guro@fb.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A9610181C43CB X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000994, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/7/20 7:36 PM, Roman Gushchin wrote: > Currently memcg_kmem_enabled() is optimized for the kernel memory > accounting being off. It was so for a long time, and arguably the > reason behind was that the kernel memory accounting was initially an > opt-in feature. However, now it's on by default on both cgroup v1 > and cgroup v2, and it's on for all cgroups. So let's switch over > to static_branch_likely() to reflect this fact. > > Unlikely there is a significant performance difference, as the cost > of a memory allocation and its accounting significantly exceeds the > cost of a jump. However, the conversion makes the code look more > logically. > > Signed-off-by: Roman Gushchin Acked-by: Vlastimil Babka > --- > include/linux/memcontrol.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index b8f52a3fed90..ab9322215b2e 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -1456,7 +1456,7 @@ void memcg_put_cache_ids(void); > > static inline bool memcg_kmem_enabled(void) > { > - return static_branch_unlikely(&memcg_kmem_enabled_key); > + return static_branch_likely(&memcg_kmem_enabled_key); > } > > static inline bool memcg_kmem_bypass(void) >