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Thu, 03 Dec 2020 11:27:10 -0500 X-MC-Unique: cTAmb5S7OcWbeNkMp5F9Fg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 06961425F7; Thu, 3 Dec 2020 16:27:09 +0000 (UTC) Received: from [10.36.113.250] (ovpn-113-250.ams2.redhat.com [10.36.113.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 214585D730; Thu, 3 Dec 2020 16:27:07 +0000 (UTC) Subject: Re: [PATCH] mm/page_isolation: do not isolate the max order page To: Muchun Song , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20201202122114.75316-1-songmuchun@bytedance.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 3 Dec 2020 17:27:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201202122114.75316-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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 02.12.20 13:21, Muchun Song wrote: > The max order page has no buddy page and never merge to other order. > So isolating and then freeing it is pointless. > > Signed-off-by: Muchun Song > --- > mm/page_isolation.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index a254e1f370a3..bddf788f45bf 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -88,7 +88,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) > */ > if (PageBuddy(page)) { > order = buddy_order(page); > - if (order >= pageblock_order) { > + if (order >= pageblock_order && order < MAX_ORDER - 1) { > pfn = page_to_pfn(page); > buddy_pfn = __find_buddy_pfn(pfn, order); > buddy = page + (buddy_pfn - pfn); > Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb