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=-2.5 required=3.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A7301C3A5A3 for ; Tue, 27 Aug 2019 05:43:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6C3FF20828 for ; Tue, 27 Aug 2019 05:43:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C3FF20828 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1D17B6B000A; Tue, 27 Aug 2019 01:43:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 15C466B000C; Tue, 27 Aug 2019 01:43:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 04A306B000D; Tue, 27 Aug 2019 01:43:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0075.hostedemail.com [216.40.44.75]) by kanga.kvack.org (Postfix) with ESMTP id D68D76B000A for ; Tue, 27 Aug 2019 01:43:42 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 7F2A6824CA38 for ; Tue, 27 Aug 2019 05:43:42 +0000 (UTC) X-FDA: 75867115884.03.stew71_5a8b091cec02c X-HE-Tag: stew71_5a8b091cec02c X-Filterd-Recvd-Size: 4214 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Tue, 27 Aug 2019 05:43:42 +0000 (UTC) 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 20079ACC2; Tue, 27 Aug 2019 05:43:38 +0000 (UTC) Date: Tue, 27 Aug 2019 07:43:37 +0200 From: Michal Hocko To: Pankaj Suryawanshi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , pankaj.suryawanshi@einfochips.com Subject: Re: PageBlocks and Migrate Types Message-ID: <20190827054337.GK7538@dhcp22.suse.cz> References: <20190822125231.GJ12785@dhcp22.suse.cz> <20190826070436.GA7538@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon 26-08-19 22:35:08, Pankaj Suryawanshi wrote: > On Mon, Aug 26, 2019 at 12:34 PM Michal Hocko wrote: > > > > On Thu 22-08-19 23:54:19, Pankaj Suryawanshi wrote: > > > On Thu, Aug 22, 2019 at 6:22 PM Michal Hocko wrote: > > > > > > > > On Wed 21-08-19 22:23:44, Pankaj Suryawanshi wrote: > > > > > Hello, > > > > > > > > > > 1. What are Pageblocks and migrate types(MIGRATE_CMA) in Linux > memory ? > > > > > > > > Pageblocks are a simple grouping of physically contiguous pages with > > > > common set of flags. I haven't checked closely recently so I might > > > > misremember but my recollection is that only the migrate type is > stored > > > > there. Normally we would store that information into page flags but > > > > there is not enough room there. > > > > > > > > MIGRATE_CMA represent pages allocated for the CMA allocator. There are > > > > other migrate types denoting unmovable/movable allocations or pages > that > > > > are isolated from the page allocator. > > > > > > > > Very broadly speaking, the migrate type groups pages with similar > > > > movability properties to reduce fragmentation that compaction cannot > > > > do anything about because there are objects of different properti > > > > around. Please note that pageblock might contain objects of a > different > > > > migrate type in some cases (e.g. low on memory). > > > > > > > > Have a look at gfpflags_to_migratetype and how the gfp mask is > converted > > > > to a migratetype for the allocation. Also follow different > MIGRATE_$TYPE > > > > to see how it is used in the code. > > > > > > > > > How many movable/unmovable pages are defined by default? > > > > > > > > There is nothing like that. It depends on how many objects of a > specific > > > > type are allocated. > > > > > > > > > It means that it started creating pageblocks after allocation of > > > different objects, but from which block it allocate initially when > > > there is nothing like pageblocks ? (when memory subsystem up) > > > > Pageblocks are just a way to group physically contiguous pages. They > > just exist along with the physically contiguous memory. The migrate type > > for most of the memory is set to MIGRATE_MOVABLE. Portion of the memory > > might be reserved by CMA then that memory has MIGRATE_CMA. Following > > set_pageblock_migratetype call paths will give you a good picture. > > it means if i have 4096 continuous pages = 1 pageblock > then all the 4096 pages of same type. but if any one page is different than > block type then ? it changed the block type or something else ? That really depends on the specific migrate type. CMA, ISOLATE migrate types are all or nothing IIRC. I would have to check the code to tell exactly when MOVABLE/UNMOVABLE pageblocks transitions are done. steal_suitable_fallback sounds like a good start to look at. -- Michal Hocko SUSE Labs