From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752592AbcGSGqg (ORCPT ); Tue, 19 Jul 2016 02:46:36 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:58788 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752265AbcGSGqd (ORCPT ); Tue, 19 Jul 2016 02:46:33 -0400 X-Original-SENDERIP: 156.147.1.127 X-Original-MAILFROM: iamjoonsoo.kim@lge.com X-Original-SENDERIP: 10.177.222.138 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Tue, 19 Jul 2016 15:50:42 +0900 From: Joonsoo Kim To: Xishi Qiu Cc: Vlastimil Babka , David Rientjes , Andrew Morton , Naoya Horiguchi , Linux MM , LKML Subject: Re: [PATCH 1/2] mem-hotplug: use GFP_HIGHUSER_MOVABLE in, alloc_migrate_target() Message-ID: <20160719065042.GC17479@js1304-P5Q-DELUXE> References: <57884EAA.9030603@huawei.com> <20160718055150.GF9460@js1304-P5Q-DELUXE> <578C8C8A.8000007@huawei.com> <7ce4a7ac-07aa-6a81-48c2-91c4a9355778@suse.cz> <578C93CF.50509@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <578C93CF.50509@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 18, 2016 at 04:31:11PM +0800, Xishi Qiu wrote: > On 2016/7/18 16:05, Vlastimil Babka wrote: > > > On 07/18/2016 10:00 AM, Xishi Qiu wrote: > >> On 2016/7/18 13:51, Joonsoo Kim wrote: > >> > >>> On Fri, Jul 15, 2016 at 10:47:06AM +0800, Xishi Qiu wrote: > >>>> alloc_migrate_target() is called from migrate_pages(), and the page > >>>> is always from user space, so we can add __GFP_HIGHMEM directly. > >>> > >>> No, all migratable pages are not from user space. For example, > >>> blockdev file cache has __GFP_MOVABLE and migratable but it has no > >>> __GFP_HIGHMEM and __GFP_USER. > >>> > >> > >> Hi Joonsoo, > >> > >> So the original code "gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;" > >> is not correct? > > > > It's not incorrect. GFP_USER just specifies some reclaim flags, and may perhaps restrict allocation through __GFP_HARDWALL, where the original > > page could have been allocated without the restriction. But it doesn't put the place in an unexpected address range, as placing a non-highmem page into highmem could. __GFP_MOVABLE then just controls a heuristic for placement within a zone. > > > >>> And, zram's memory isn't GFP_HIGHUSER_MOVABLE but has __GFP_MOVABLE. > >>> > >> > >> Can we distinguish __GFP_MOVABLE or GFP_HIGHUSER_MOVABLE when doing > >> mem-hotplug? > > > > I don't understand the question here, can you rephrase with more detail? Thanks. > > > > Hi Joonsoo, Above is answered by Vlastimil. :) > When we do memory offline, and the zone is movable zone, > can we use "alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);" to alloc a > new page? the nid is the next node. I don't know much about memory offline, but, AFAIK, memory offline could happen on non-movable zone like as ZONE_NORMAL. Perhaps, you can add "if zone of the page is movable zone then alloc with GFP_HIGHUSER_MOVABLE". Thanks.