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[195.135.220.15]) by mx.google.com with ESMTPS id h6si1469217eja.76.2019.03.12.08.06.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Mar 2019 08:06:05 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B9D05B168; Tue, 12 Mar 2019 15:06:04 +0000 (UTC) Date: Tue, 12 Mar 2019 16:06:04 +0100 From: Michal Hocko To: Qian Cai Cc: akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH] mm/hotplug: don't reset pagetype flags for offline Message-ID: <20190312150604.GT5721@dhcp22.suse.cz> References: <20190310200102.88014-1-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190310200102.88014-1-cai@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) 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 10-03-19 16:01:02, Qian Cai wrote: > The commit f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded > memory to zones until online") introduced move_pfn_range_to_zone() which > calls memmap_init_zone() during onlining a memory block. > memmap_init_zone() will reset pagetype flags and makes migrate type to > be MOVABLE. > > However, in __offline_pages(), it also call undo_isolate_page_range() > after offline_isolated_pages() to do the same thing. Due to > the commit 2ce13640b3f4 ("mm: __first_valid_page skip over offline > pages") changed __first_valid_page() to skip offline pages, > undo_isolate_page_range() here just waste CPU cycles looping around the > offlining PFN range while doing nothing, because __first_valid_page() > will return NULL as offline_isolated_pages() has already marked all > memory sections within the pfn range as offline via > offline_mem_sections(). > > Also, after calling the "useless" undo_isolate_page_range() here, it > reaches the point of no returning by notifying MEM_OFFLINE. Those pages > will be marked as MIGRATE_MOVABLE again once onlining. In addition, fix > an incorrect comment along the way. > > Signed-off-by: Qian Cai Well spotted. Thanks! Acked-by: Michal Hocko > --- > mm/memory_hotplug.c | 2 -- > mm/sparse.c | 2 +- > 2 files changed, 1 insertion(+), 3 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 6b05576fb4ec..46017040b2f8 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1655,8 +1655,6 @@ static int __ref __offline_pages(unsigned long start_pfn, > /* Ok, all of our target is isolated. > We cannot do rollback at this point. */ > offline_isolated_pages(start_pfn, end_pfn); > - /* reset pagetype flags and makes migrate type to be MOVABLE */ > - undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); > /* removal success */ > adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages); > zone->present_pages -= offlined_pages; > diff --git a/mm/sparse.c b/mm/sparse.c > index 77a0554fa5bd..b3771f35a0ed 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -556,7 +556,7 @@ void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > } > > #ifdef CONFIG_MEMORY_HOTREMOVE > -/* Mark all memory sections within the pfn range as online */ > +/* Mark all memory sections within the pfn range as offline */ > void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > { > unsigned long pfn; > -- > 2.17.2 (Apple Git-113) -- Michal Hocko SUSE Labs