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[217.140.101.70]) by mx.google.com with ESMTP id t32si1744111edd.442.2019.03.21.01.13.45 for ; Thu, 21 Mar 2019 01:13:45 -0700 (PDT) Received-SPF: pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DFB4080D; Thu, 21 Mar 2019 01:13:44 -0700 (PDT) Received: from [10.162.42.102] (p8cg001049571a15.blr.arm.com [10.162.42.102]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D22803F71A; Thu, 21 Mar 2019 01:13:42 -0700 (PDT) Subject: Re: [PATCH] mm/isolation: Remove redundant pfn_valid_within() in __first_valid_page() To: Michal Hocko Cc: Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, mike.kravetz@oracle.com, osalvador@suse.de, akpm@linux-foundation.org References: <1553141595-26907-1-git-send-email-anshuman.khandual@arm.com> <8AB57711-48C0-4D95-BC5F-26B266DC3AE8@nvidia.com> <20190321080702.GG8696@dhcp22.suse.cz> From: Anshuman Khandual Message-ID: <8a6b3968-a315-07ce-0491-2a5acdd49ab4@arm.com> Date: Thu, 21 Mar 2019 13:43:40 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190321080702.GG8696@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 03/21/2019 01:37 PM, Michal Hocko wrote: > On Thu 21-03-19 11:03:18, Anshuman Khandual wrote: >> >> >> On 03/21/2019 10:31 AM, Zi Yan wrote: >>> On 20 Mar 2019, at 21:13, Anshuman Khandual wrote: >>> >>>> pfn_valid_within() calls pfn_valid() when CONFIG_HOLES_IN_ZONE making it >>>> redundant for both definitions (w/wo CONFIG_MEMORY_HOTPLUG) of the helper >>>> pfn_to_online_page() which either calls pfn_valid() or pfn_valid_within(). >>>> pfn_valid_within() being 1 when !CONFIG_HOLES_IN_ZONE is irrelevant either >>>> way. This does not change functionality. >>>> >>>> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages") >>> >>> I would not say this patch fixes the commit 2ce13640b3f4 from 2017, >>> because the pfn_valid_within() in pfn_to_online_page() was introduced by >>> a recent commit b13bc35193d9e last month. :) >> >> Right, will update the tag with this commit. > > The patch is correct but I wouldn't bother to add Fixes tag at all. The > current code is obviously not incorrect. Do you see any actual Sure. > performance issue? > No. Just from code inspection. pfn_valid() is anyways expensive on arm64 because of the memblock search so why to make it redundant as well.