From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753343AbdJSMV0 (ORCPT ); Thu, 19 Oct 2017 08:21:26 -0400 Received: from mx2.suse.de ([195.135.220.15]:56854 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753163AbdJSMVX (ORCPT ); Thu, 19 Oct 2017 08:21:23 -0400 Date: Thu, 19 Oct 2017 14:21:18 +0200 From: Michal Hocko To: Joonsoo Kim Cc: linux-mm@kvack.org, Michael Ellerman , Vlastimil Babka , Andrew Morton , KAMEZAWA Hiroyuki , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Igor Mammedov , Vitaly Kuznetsov , LKML Subject: Re: [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Message-ID: <20171019122118.y6cndierwl2vnguj@dhcp22.suse.cz> References: <20171013115835.zaehapuucuzl2vlv@dhcp22.suse.cz> <20171013120013.698-1-mhocko@kernel.org> <20171019025111.GA3852@js1304-P5Q-DELUXE> <20171019071503.e7w5fo35lsq6ca54@dhcp22.suse.cz> <20171019073355.GA4486@js1304-P5Q-DELUXE> <20171019082041.5zudpqacaxjhe4gw@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171019082041.5zudpqacaxjhe4gw@dhcp22.suse.cz> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 19-10-17 10:20:41, Michal Hocko wrote: > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > [...] > > > > Hello, > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > itself isn't migrateable. So, after a single page is allocated through > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > fail because it requires isolating the pageblock. > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > has_unmovable_pages to return false here even though the memory is not > > > movable? This sounds really strange to me and kind of abuse of this > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > alloc_contig_range() -> start_isolate_page_range() -> > > set_migratetype_isolate() -> has_unmovable_pages() > > I see. It seems that the CMA and memory hotplug have a very different > view on what should happen during isolation. > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > specified. > > Can we use the migratetype argument and do the special thing for > MIGRATE_CMA? Like the following diff? And with the full changelog. --- >>From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 19 Oct 2017 14:14:02 +0200 Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in has_unmovable_pages Joonsoo has noticed that "mm: drop migrate type checks from has_unmovable_pages" would break CMA allocator because it relies on has_unmovable_pages returning false even for CMA pageblocks which in fact don't have to be movable: alloc_contig_range start_isolate_page_range set_migratetype_isolate has_unmovable_pages This is a result of the code sharing between CMA and memory hotplug while each one has a different idea of what has_unmovable_pages should return. This is unfortunate but fixing it properly would require a lot of code duplication. Fix the issue by introducing the requested migrate type argument and special case MIGRATE_CMA case where CMA page blocks are handled properly. This will work for memory hotplug because it requires MIGRATE_MOVABLE. Reported-by: Joonsoo Kim Signed-off-by: Michal Hocko --- include/linux/page-isolation.h | 2 +- mm/page_alloc.c | 12 +++++++++++- mm/page_isolation.c | 10 +++++----- 3 files changed, 17 insertions(+), 7 deletions(-) diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h index d4cd2014fa6f..fa9db0c7b54e 100644 --- a/include/linux/page-isolation.h +++ b/include/linux/page-isolation.h @@ -30,7 +30,7 @@ static inline bool is_migrate_isolate(int migratetype) #endif bool has_unmovable_pages(struct zone *zone, struct page *page, int count, - bool skip_hwpoisoned_pages); + int migratetype, bool skip_hwpoisoned_pages); void set_pageblock_migratetype(struct page *page, int migratetype); int move_freepages_block(struct zone *zone, struct page *page, int migratetype, int *num_movable); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5b4d85ae445c..259aeb22462f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7344,6 +7344,7 @@ void *__init alloc_large_system_hash(const char *tablename, * race condition. So you can't expect this function should be exact. */ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, + int migratetype, bool skip_hwpoisoned_pages) { unsigned long pfn, iter, found; @@ -7356,6 +7357,15 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, if (zone_idx(zone) == ZONE_MOVABLE) return false; + /* + * CMA allocations (alloc_contig_range) really need to mark isolate + * CMA pageblocks even when they are not movable in fact so consider + * them movable here. + */ + if (is_migrate_cma(migratetype) && + is_migrate_cma(get_pageblock_migratetype(page))) + return false; + pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { unsigned long check = pfn + iter; @@ -7441,7 +7451,7 @@ bool is_pageblock_removable_nolock(struct page *page) if (!zone_spans_pfn(zone, pfn)) return false; - return !has_unmovable_pages(zone, page, 0, true); + return !has_unmovable_pages(zone, page, 0, MIGRATE_MOVABLE, true); } #if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA) diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 757410d9f758..8616f5332c77 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -14,7 +14,7 @@ #define CREATE_TRACE_POINTS #include -static int set_migratetype_isolate(struct page *page, +static int set_migratetype_isolate(struct page *page, int migratetype, bool skip_hwpoisoned_pages) { struct zone *zone; @@ -51,7 +51,7 @@ static int set_migratetype_isolate(struct page *page, * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. * We just check MOVABLE pages. */ - if (!has_unmovable_pages(zone, page, arg.pages_found, + if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype, skip_hwpoisoned_pages)) ret = 0; @@ -63,14 +63,14 @@ static int set_migratetype_isolate(struct page *page, out: if (!ret) { unsigned long nr_pages; - int migratetype = get_pageblock_migratetype(page); + int mt = get_pageblock_migratetype(page); set_pageblock_migratetype(page, MIGRATE_ISOLATE); zone->nr_isolate_pageblock++; nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE, NULL); - __mod_zone_freepage_state(zone, -nr_pages, migratetype); + __mod_zone_freepage_state(zone, -nr_pages, mt); } spin_unlock_irqrestore(&zone->lock, flags); @@ -182,7 +182,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, pfn += pageblock_nr_pages) { page = __first_valid_page(pfn, pageblock_nr_pages); if (page && - set_migratetype_isolate(page, skip_hwpoisoned_pages)) { + set_migratetype_isolate(page, migratetype, skip_hwpoisoned_pages)) { undo_pfn = pfn; goto undo; } -- 2.14.2 -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 5FB3E6B0261 for ; Thu, 19 Oct 2017 08:21:24 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id g10so2813578wrg.6 for ; Thu, 19 Oct 2017 05:21:24 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id u12si11632827wre.448.2017.10.19.05.21.22 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 19 Oct 2017 05:21:22 -0700 (PDT) Date: Thu, 19 Oct 2017 14:21:18 +0200 From: Michal Hocko Subject: Re: [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Message-ID: <20171019122118.y6cndierwl2vnguj@dhcp22.suse.cz> References: <20171013115835.zaehapuucuzl2vlv@dhcp22.suse.cz> <20171013120013.698-1-mhocko@kernel.org> <20171019025111.GA3852@js1304-P5Q-DELUXE> <20171019071503.e7w5fo35lsq6ca54@dhcp22.suse.cz> <20171019073355.GA4486@js1304-P5Q-DELUXE> <20171019082041.5zudpqacaxjhe4gw@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171019082041.5zudpqacaxjhe4gw@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: linux-mm@kvack.org, Michael Ellerman , Vlastimil Babka , Andrew Morton , KAMEZAWA Hiroyuki , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Igor Mammedov , Vitaly Kuznetsov , LKML On Thu 19-10-17 10:20:41, Michal Hocko wrote: > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > [...] > > > > Hello, > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > itself isn't migrateable. So, after a single page is allocated through > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > fail because it requires isolating the pageblock. > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > has_unmovable_pages to return false here even though the memory is not > > > movable? This sounds really strange to me and kind of abuse of this > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > alloc_contig_range() -> start_isolate_page_range() -> > > set_migratetype_isolate() -> has_unmovable_pages() > > I see. It seems that the CMA and memory hotplug have a very different > view on what should happen during isolation. > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > specified. > > Can we use the migratetype argument and do the special thing for > MIGRATE_CMA? Like the following diff? And with the full changelog. ---