Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757510AbcCDEcJ (ORCPT ); Thu, 3 Mar 2016 23:32:09 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:52984 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753440AbcCDEcH (ORCPT ); Thu, 3 Mar 2016 23:32:07 -0500 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: iamjoonsoo.kim@lge.com X-Original-SENDERIP: 10.177.222.138 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Fri, 4 Mar 2016 13:32:32 +0900 From: Joonsoo Kim To: Hanjun Guo Cc: Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Sasha Levin , Laura Abbott , qiuxishi , Catalin Marinas , Will Deacon , Arnd Bergmann , "thunder.leizhen@huawei.com" , dingtinahong , chenjie6@huawei.com, "linux-mm@kvack.org" Subject: Re: Suspicious error for CMA stress test Message-ID: <20160304043232.GC12036@js1304-P5Q-DELUXE> References: <56D6F008.1050600@huawei.com> <56D79284.3030009@redhat.com> <56D832BD.5080305@huawei.com> <20160304020232.GA12036@js1304-P5Q-DELUXE> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160304020232.GA12036@js1304-P5Q-DELUXE> 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 Content-Length: 5407 Lines: 134 On Fri, Mar 04, 2016 at 11:02:33AM +0900, Joonsoo Kim wrote: > On Thu, Mar 03, 2016 at 08:49:01PM +0800, Hanjun Guo wrote: > > On 2016/3/3 15:42, Joonsoo Kim wrote: > > > 2016-03-03 10:25 GMT+09:00 Laura Abbott : > > >> (cc -mm and Joonsoo Kim) > > >> > > >> > > >> On 03/02/2016 05:52 AM, Hanjun Guo wrote: > > >>> Hi, > > >>> > > >>> I came across a suspicious error for CMA stress test: > > >>> > > >>> Before the test, I got: > > >>> -bash-4.3# cat /proc/meminfo | grep Cma > > >>> CmaTotal: 204800 kB > > >>> CmaFree: 195044 kB > > >>> > > >>> > > >>> After running the test: > > >>> -bash-4.3# cat /proc/meminfo | grep Cma > > >>> CmaTotal: 204800 kB > > >>> CmaFree: 6602584 kB > > >>> > > >>> So the freed CMA memory is more than total.. > > >>> > > >>> Also the the MemFree is more than mem total: > > >>> > > >>> -bash-4.3# cat /proc/meminfo > > >>> MemTotal: 16342016 kB > > >>> MemFree: 22367268 kB > > >>> MemAvailable: 22370528 kB > > [...] > > >> > > >> I played with this a bit and can see the same problem. The sanity > > >> check of CmaFree < CmaTotal generally triggers in > > >> __move_zone_freepage_state in unset_migratetype_isolate. > > >> This also seems to be present as far back as v4.0 which was the > > >> first version to have the updated accounting from Joonsoo. > > >> Were there known limitations with the new freepage accounting, > > >> Joonsoo? > > > I don't know. I also played with this and looks like there is > > > accounting problem, however, for my case, number of free page is slightly less > > > than total. I will take a look. > > > > > > Hanjun, could you tell me your malloc_size? I tested with 1 and it doesn't > > > look like your case. > > > > I tested with malloc_size with 2M, and it grows much bigger than 1M, also I > > did some other test: > > Thanks! Now, I can re-generate erronous situation you mentioned. > > > > > - run with single thread with 100000 times, everything is fine. > > > > - I hack the cam_alloc() and free as below [1] to see if it's lock issue, with > > the same test with 100 multi-thread, then I got: > > [1] would not be sufficient to close this race. > > Try following things [A]. And, for more accurate test, I changed code a bit more > to prevent kernel page allocation from cma area [B]. This will prevent kernel > page allocation from cma area completely so we can focus cma_alloc/release race. > > Although, this is not correct fix, it could help that we can guess > where the problem is. More correct fix is something like below. Please test it. It checks problematic buddy merging and prevent it. I will try to find another way that is less intrusive for freepath performance. Thanks. ---------------->8----------------------- >From 855cb11368487a0f02a5ad5b3d9de375dfbb061c Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Fri, 4 Mar 2016 13:28:17 +0900 Subject: [PATCH] mm/cma: fix race Signed-off-by: Joonsoo Kim --- mm/page_alloc.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c6c38ed..a01c3b5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -620,8 +620,8 @@ static inline void rmv_page_order(struct page *page) * * For recording page's order, we use page_private(page). */ -static inline int page_is_buddy(struct page *page, struct page *buddy, - unsigned int order) +static inline int page_is_buddy(struct zone *zone, struct page *page, + struct page *buddy, unsigned int order) { if (!pfn_valid_within(page_to_pfn(buddy))) return 0; @@ -644,6 +644,12 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, if (page_zone_id(page) != page_zone_id(buddy)) return 0; + if (IS_ENABLED(CONFIG_CMA) && + has_isolate_pageblock(zone) && + order >= pageblock_order && + is_migrate_isolate(get_pageblock_migratetype(buddy))) + return 0; + VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); return 1; @@ -711,7 +717,7 @@ static inline void __free_one_page(struct page *page, while (order < max_order - 1) { buddy_idx = __find_buddy_index(page_idx, order); buddy = page + (buddy_idx - page_idx); - if (!page_is_buddy(page, buddy, order)) + if (!page_is_buddy(zone, page, buddy, order)) break; /* * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page, @@ -745,7 +751,7 @@ static inline void __free_one_page(struct page *page, higher_page = page + (combined_idx - page_idx); buddy_idx = __find_buddy_index(combined_idx, order + 1); higher_buddy = higher_page + (buddy_idx - combined_idx); - if (page_is_buddy(higher_page, higher_buddy, order + 1)) { + if (page_is_buddy(zone, higher_page, higher_buddy, order + 1)) { list_add_tail(&page->lru, &zone->free_area[order].free_list[migratetype]); goto out; -- 1.9.1