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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 EFBAEC3A5A3 for ; Tue, 27 Aug 2019 05:43:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1A9D217F5 for ; Tue, 27 Aug 2019 05:43:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566884621; bh=chMysLLacYvgN/hPklsN3lcWmtRimfzfHVWE42kvjG8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=C0IMvDnsUVDvFS13ujiC3Y0tIdKmB2psNkhPTek3zQdjUQAstjYq3P1GDxtDb1UVO j1TTaFYJwMuSXPvw93X8cMCOWGgoiwjas1aoT6Bm0zzsmx/Qz/vUnTaXa0TWuYYEEW 9ax+qNwM3774h6YQZ0tTNR2IBz3qabLLrrGv0wl8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728053AbfH0Fnk (ORCPT ); Tue, 27 Aug 2019 01:43:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:49164 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725874AbfH0Fnk (ORCPT ); Tue, 27 Aug 2019 01:43:40 -0400 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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