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 D6C1EC3A59E for ; Mon, 26 Aug 2019 07:04:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A63882080C for ; Mon, 26 Aug 2019 07:04:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A63882080C 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 3F7746B0529; Mon, 26 Aug 2019 03:04:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A8716B052B; Mon, 26 Aug 2019 03:04:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2BDCA6B052C; Mon, 26 Aug 2019 03:04:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0121.hostedemail.com [216.40.44.121]) by kanga.kvack.org (Postfix) with ESMTP id 065AD6B0529 for ; Mon, 26 Aug 2019 03:04:40 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id A400A4FE2 for ; Mon, 26 Aug 2019 07:04:40 +0000 (UTC) X-FDA: 75863691120.24.grip11_bb083674c15f X-HE-Tag: grip11_bb083674c15f X-Filterd-Recvd-Size: 3420 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Mon, 26 Aug 2019 07:04:40 +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 0BFC4AD7F; Mon, 26 Aug 2019 07:04:37 +0000 (UTC) Date: Mon, 26 Aug 2019 09:04:36 +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: <20190826070436.GA7538@dhcp22.suse.cz> References: <20190822125231.GJ12785@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 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. > Pageblocks and its type dynamically changes ? Yes as the purpose of the underlying memory for the block changes. -- Michal Hocko SUSE Labs