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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 DAC8AC0044D for ; Wed, 11 Mar 2020 23:04:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD0B72074F for ; Wed, 11 Mar 2020 23:04:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731468AbgCKXEF (ORCPT ); Wed, 11 Mar 2020 19:04:05 -0400 Received: from mx2.suse.de ([195.135.220.15]:40902 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729739AbgCKXEF (ORCPT ); Wed, 11 Mar 2020 19:04:05 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 67014AC61; Wed, 11 Mar 2020 23:04:02 +0000 (UTC) Subject: Re: [PATCH] mm,page_alloc,cma: conditionally prefer cma pageblocks for movable allocations To: Roman Gushchin Cc: Rik van Riel , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Qian Cai , Mel Gorman , Anshuman Khandual , Joonsoo Kim References: <20200306150102.3e77354b@imladris.surriel.com> <20200307143849.a2fcb81a9626dad3ee46471f@linux-foundation.org> <2f3e2cde7b94dfdb8e1f0532d1074e07ef675bc4.camel@surriel.com> <5ed7f24b-d21b-75a1-ff74-49a9e21a7b39@suse.cz> <20200311225832.GA178154@carbon.DHCP.thefacebook.com> From: Vlastimil Babka Message-ID: <55f366be-ed3e-7b57-0fae-54845574d98a@suse.cz> Date: Thu, 12 Mar 2020 00:03:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200311225832.GA178154@carbon.DHCP.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/11/20 11:58 PM, Roman Gushchin wrote: >> >> I agree it should be in the noise. But please do put it behind CONFIG_CMA >> #ifdef. My x86_64 desktop distro kernel doesn't have CONFIG_CMA. Even if this is >> effectively no-op with __rmqueue_cma_fallback() returning NULL immediately, I >> think the compiler cannot eliminate the two zone_page_state()'s which are >> atomic_long_read(), even if it's just ultimately READ_ONCE() here, that's a >> volatile cast which means elimination not possible AFAIK? Other architectures >> might be even more involved. > > I agree. > > Andrew, > can you, please, squash the following diff into the patch? Thanks, then please add to the result Acked-by: Vlastimil Babka > Thank you! > > -- > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7d9067b75dcb..bc65931b3901 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2767,6 +2767,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, > { > struct page *page; > > +#ifdef CONFIG_CMA > /* > * Balance movable allocations between regular and CMA areas by > * allocating from CMA when over half of the zone's free memory > @@ -2779,6 +2780,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, > if (page) > return page; > } > +#endif > retry: > page = __rmqueue_smallest(zone, order, migratetype); > if (unlikely(!page)) { > >