From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx139.postini.com [74.125.245.139]) by kanga.kvack.org (Postfix) with SMTP id 64D376B006C for ; Mon, 12 Dec 2011 09:52:02 -0500 (EST) Received: by vcbfk26 with SMTP id fk26so5103409vcb.14 for ; Mon, 12 Dec 2011 06:52:01 -0800 (PST) Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes Subject: Re: [PATCH 03/11] mm: mmzone: introduce zone_pfn_same_memmap() References: <1321634598-16859-1-git-send-email-m.szyprowski@samsung.com> <1321634598-16859-4-git-send-email-m.szyprowski@samsung.com> <20111212141953.GD3277@csn.ul.ie> <20111212144030.GF3277@csn.ul.ie> Date: Mon, 12 Dec 2011 15:51:55 +0100 MIME-Version: 1.0 Content-Transfer-Encoding: Quoted-Printable From: "Michal Nazarewicz" Message-ID: In-Reply-To: <20111212144030.GF3277@csn.ul.ie> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Dave Hansen Cc: Marek Szyprowski , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org, Kyungmin Park , Russell King , Andrew Morton , KAMEZAWA Hiroyuki , Ankita Garg , Daniel Walker , Arnd Bergmann , Jesse Barker , Jonathan Corbet , Shariq Hasnain , Chunsang Jeong > On Fri, Nov 18, 2011 at 05:43:10PM +0100, Marek Szyprowski wrote: >> From: Michal Nazarewicz >> diff --git a/mm/compaction.c b/mm/compaction.c >> index 6afae0e..09c9702 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -111,7 +111,10 @@ skip: >> >> next: >> pfn +=3D isolated; >> - page +=3D isolated; >> + if (zone_pfn_same_memmap(pfn - isolated, pfn)) >> + page +=3D isolated; >> + else >> + page =3D pfn_to_page(pfn); >> } On Mon, 12 Dec 2011 15:19:53 +0100, Mel Gorman wrote: > Is this necessary? > > We are isolating pages, the largest of which is a MAX_ORDER_NR_PAGES > page. [...] On Mon, 12 Dec 2011 15:40:30 +0100, Mel Gorman wrote: > To be clear, I'm referring to a single page being isolated here. It ma= y > or may not be a high-order page but it's still going to be less then > MAX_ORDER_NR_PAGES so you should be able check when a new block is > entered and pfn_to_page is necessary. Do you mean something like: if (same pageblock) just do arithmetic; else use pfn_to_page; ? I've discussed it with Dave and he suggested that approach as an optimisation since in some configurations zone_pfn_same_memmap() is always true thus compiler will strip the else part, whereas same pageblock test will be false on occasions regardless of kernel configuration. -- = Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=3D./ `o ..o | Computer Science, Micha=C5=82 =E2=80=9Cmina86=E2=80=9D Nazarewicz= (o o) ooo +------------------ooO--(_)--Ooo-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org