Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932218AbcCHByx (ORCPT ); Mon, 7 Mar 2016 20:54:53 -0500 Received: from szxga01-in.huawei.com ([58.251.152.64]:22358 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753367AbcCHByn (ORCPT ); Mon, 7 Mar 2016 20:54:43 -0500 Subject: Re: Suspicious error for CMA stress test To: Laura Abbott , Joonsoo Kim , Hanjun Guo References: <56D6F008.1050600@huawei.com> <56D79284.3030009@redhat.com> <56D832BD.5080305@huawei.com> <20160304020232.GA12036@js1304-P5Q-DELUXE> <20160304043232.GC12036@js1304-P5Q-DELUXE> <56D92595.60709@huawei.com> <20160304063807.GA13317@js1304-P5Q-DELUXE> <56D93ABE.9070406@huawei.com> <20160307043442.GB24602@js1304-P5Q-DELUXE> <56DD38E7.3050107@huawei.com> <56DDCB86.4030709@redhat.com> CC: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Sasha Levin , Laura Abbott , qiuxishi , Catalin Marinas , Will Deacon , Arnd Bergmann , dingtinahong , , "linux-mm@kvack.org" From: "Leizhen (ThunderTown)" Message-ID: <56DE30CB.7020207@huawei.com> Date: Tue, 8 Mar 2016 09:54:19 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <56DDCB86.4030709@redhat.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.23.164] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020201.56DE30DB.0128,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: ed41f6e7d2a049fd2d64899ea62c1475 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8885 Lines: 204 On 2016/3/8 2:42, Laura Abbott wrote: > On 03/07/2016 12:16 AM, Leizhen (ThunderTown) wrote: >> >> >> On 2016/3/7 12:34, Joonsoo Kim wrote: >>> On Fri, Mar 04, 2016 at 03:35:26PM +0800, Hanjun Guo wrote: >>>> On 2016/3/4 14:38, Joonsoo Kim wrote: >>>>> On Fri, Mar 04, 2016 at 02:05:09PM +0800, Hanjun Guo wrote: >>>>>> On 2016/3/4 12:32, Joonsoo Kim wrote: >>>>>>> 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. >>>>>> Hmm, this is not working: >>>>> Sad to hear that. >>>>> >>>>> Could you tell me your system's MAX_ORDER and pageblock_order? >>>>> >>>> >>>> MAX_ORDER is 11, pageblock_order is 9, thanks for your help! >>> >>> Hmm... that's same with me. >>> >>> Below is similar fix that prevents buddy merging when one of buddy's >>> migrate type, but, not both, is MIGRATE_ISOLATE. In fact, I have >>> no idea why previous fix (more correct fix) doesn't work for you. >>> (It works for me.) But, maybe there is a bug on the fix >>> so I make new one which is more general form. Please test it. >> >> Hi, >> Hanjun Guo has gone to Tailand on business, so I help him to run this patch. The result >> shows that the count of "CmaFree:" is OK now. But sometimes printed some information as below: >> >> alloc_contig_range: [28500, 28600) PFNs busy >> alloc_contig_range: [28300, 28380) PFNs busy >> > > Those messages aren't necessarily a problem. Those messages indicate that OK. > those pages weren't able to be isolated. Given the test here is a > concurrency test, I suspect some concurrent allocation or free prevented > isolation which is to be expected some times. I'd only be concerned if > seeing those messages cause allocation failure or some other notable impact. I chose memory block size: 512K, 1M, 2M ran serveral times, there was no memory allocation failure. > > Thanks, > Laura > >>> >>> Thanks. >>> >>> ---------->8------------- >>> >From dd41e348572948d70b935fc24f82c096ff0fb417 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 | 33 +++++++++++++++++++-------------- >>> 1 file changed, 19 insertions(+), 14 deletions(-) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index c6c38ed..d80d071 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 +644,20 @@ 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) && >>> + unlikely(has_isolate_pageblock(zone)) && >>> + unlikely(order >= pageblock_order)) { >>> + int page_mt, buddy_mt; >>> + >>> + page_mt = get_pageblock_migratetype(page); >>> + buddy_mt = get_pageblock_migratetype(buddy); >>> + >>> + if (page_mt != buddy_mt && >>> + (is_migrate_isolate(page_mt) || >>> + is_migrate_isolate(buddy_mt))) >>> + return 0; >>> + } >>> + >>> VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); >>> >>> return 1; >>> @@ -691,17 +705,8 @@ static inline void __free_one_page(struct page *page, >>> VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page); >>> >>> VM_BUG_ON(migratetype == -1); >>> - if (is_migrate_isolate(migratetype)) { >>> - /* >>> - * We restrict max order of merging to prevent merge >>> - * between freepages on isolate pageblock and normal >>> - * pageblock. Without this, pageblock isolation >>> - * could cause incorrect freepage accounting. >>> - */ >>> - max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1); >>> - } else { >>> + if (!is_migrate_isolate(migratetype)) >>> __mod_zone_freepage_state(zone, 1 << order, migratetype); >>> - } >>> >>> page_idx = pfn & ((1 << max_order) - 1); >>> >>> @@ -711,7 +716,7 @@ 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 +750,7 @@ 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; >>> >> > > > . >