From patchwork Fri Mar 4 02:02:33 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joonsoo Kim X-Patchwork-Id: 8497681 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 09AA19F314 for ; Fri, 4 Mar 2016 02:04:28 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0F8F620260 for ; Fri, 4 Mar 2016 02:04:27 +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 DFE182010B for ; Fri, 4 Mar 2016 02:04:25 +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 1abf4c-0005Vy-76; Fri, 04 Mar 2016 02:02:34 +0000 Received: from lgeamrelo12.lge.com ([156.147.23.52]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1abf4Y-0005S7-GS for linux-arm-kernel@lists.infradead.org; Fri, 04 Mar 2016 02:02:32 +0000 Received: from unknown (HELO lgeamrelo01.lge.com) (156.147.1.125) by 156.147.23.52 with ESMTP; 4 Mar 2016 11:02:05 +0900 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Received: from unknown (HELO localhost) (10.177.222.138) by 156.147.1.125 with ESMTP; 4 Mar 2016 11:02:05 +0900 X-Original-SENDERIP: 10.177.222.138 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Fri, 4 Mar 2016 11:02:33 +0900 From: Joonsoo Kim To: Hanjun Guo Subject: Re: Suspicious error for CMA stress test Message-ID: <20160304020232.GA12036@js1304-P5Q-DELUXE> References: <56D6F008.1050600@huawei.com> <56D79284.3030009@redhat.com> <56D832BD.5080305@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <56D832BD.5080305@huawei.com> 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_180231_024399_F84094B6 X-CRM114-Status: GOOD ( 24.72 ) 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 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. Thanks. [A] diff --git a/mm/cma.c b/mm/cma.c index c003274..43ed02d 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -496,7 +496,9 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count) VM_BUG_ON(pfn + count > cma->base_pfn + cma->count); + mutex_lock(&cma_mutex); free_contig_range(pfn, count); + mutex_unlock(&cma_mutex); cma_clear_bitmap(cma, pfn, count); trace_cma_release(pfn, pages, count); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c6c38ed..1ce8a59 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2192,7 +2192,8 @@ void free_hot_cold_page(struct page *page, bool cold) * excessively into the page allocator */ if (migratetype >= MIGRATE_PCPTYPES) { - if (unlikely(is_migrate_isolate(migratetype))) { + if (is_migrate_cma(migratetype) || + unlikely(is_migrate_isolate(migratetype))) { free_one_page(zone, page, pfn, 0, migratetype); goto out; } [B] diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f2dccf9..c6c38ed 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1493,6 +1493,7 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, int alloc_flags) { int i; + bool cma = false; for (i = 0; i < (1 << order); i++) { struct page *p = page + i; @@ -1500,6 +1501,9 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, return 1; } + if (is_migrate_cma(get_pcppage_migratetype(page))) + cma = true; + set_page_private(page, 0); set_page_refcounted(page); @@ -1528,6 +1532,12 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, else clear_page_pfmemalloc(page); + if (cma) { + page_ref_dec(page); + __free_pages_ok(page, order); + return 1; + } + return 0; } @@ -1582,7 +1592,7 @@ static int fallbacks[MIGRATE_TYPES][4] = { static struct page *__rmqueue_cma_fallback(struct zone *zone, unsigned int order) { - return __rmqueue_smallest(zone, order, MIGRATE_CMA); + return NULL; } #else static inline struct page *__rmqueue_cma_fallback(struct zone *zone,