From patchwork Fri Mar 4 04:32:32 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joonsoo Kim X-Patchwork-Id: 8498351 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 8E2829F38C for ; Fri, 4 Mar 2016 04:35:50 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 7046920225 for ; Fri, 4 Mar 2016 04:35:49 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4714D2010B for ; Fri, 4 Mar 2016 04:35:48 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1abhPk-0006Bx-NR; Fri, 04 Mar 2016 04:32:32 +0000 Received: from lgeamrelo11.lge.com ([156.147.23.51]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1abhPh-0005z4-48 for linux-arm-kernel@lists.infradead.org; Fri, 04 Mar 2016 04:32:30 +0000 Received: from unknown (HELO lgeamrelo02.lge.com) (156.147.1.126) by 156.147.23.51 with ESMTP; 4 Mar 2016 13:32:05 +0900 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Received: from unknown (HELO localhost) (10.177.222.138) by 156.147.1.126 with ESMTP; 4 Mar 2016 13:32:04 +0900 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 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-Disposition: inline In-Reply-To: <20160304020232.GA12036@js1304-P5Q-DELUXE> User-Agent: Mutt/1.5.21 (2010-09-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160303_203229_637457_3554BB5C X-CRM114-Status: GOOD ( 29.22 ) X-Spam-Score: -1.9 (-) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laura Abbott , Arnd Bergmann , Catalin Marinas , "thunder.leizhen@huawei.com" , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , dingtinahong , qiuxishi , Sasha Levin , Andrew Morton , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , chenjie6@huawei.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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;