Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756454AbcCCSwX (ORCPT ); Thu, 3 Mar 2016 13:52:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43945 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751435AbcCCSwW (ORCPT ); Thu, 3 Mar 2016 13:52:22 -0500 Subject: Re: Suspicious error for CMA stress test To: Hanjun Guo , Joonsoo Kim References: <56D6F008.1050600@huawei.com> <56D79284.3030009@redhat.com> <56D832BD.5080305@huawei.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 , "thunder.leizhen@huawei.com" , dingtinahong , chenjie6@huawei.com, "linux-mm@kvack.org" From: Laura Abbott Message-ID: <56D887E1.8000602@redhat.com> Date: Thu, 3 Mar 2016 10:52:17 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <56D832BD.5080305@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4704 Lines: 137 On 03/03/2016 04:49 AM, 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: > > - 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: > > -bash-4.3# cat /proc/meminfo | grep Cma > CmaTotal: 204800 kB > CmaFree: 225112 kB > > It only increased about 30M for free, not 6G+ in previous test, although > the problem is not solved, the problem is less serious, is it a synchronization > problem? > 'only' 30M is still an issue although I think you are right about something related to synchronization. When I put the cma_mutex around free_contig_range I don't see the issue. I wonder if free of the pages is racing with the undo_isolate_page_range on overlapping ranges caused by outer_start? Thanks, Laura > Thanks > Hanjun > > [1]: > index ea506eb..4447494 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -379,6 +379,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > if (!count) > return NULL; > > + mutex_lock(&cma_mutex); > mask = cma_bitmap_aligned_mask(cma, align); > offset = cma_bitmap_aligned_offset(cma, align); > bitmap_maxno = cma_bitmap_maxno(cma); > @@ -402,17 +403,16 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > mutex_unlock(&cma->lock); > > pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit); > - mutex_lock(&cma_mutex); > ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA); > - mutex_unlock(&cma_mutex); > if (ret == 0) { > page = pfn_to_page(pfn); > break; > } > > cma_clear_bitmap(cma, pfn, count); > - if (ret != -EBUSY) > + if (ret != -EBUSY) { > break; > + } > > pr_debug("%s(): memory range at %p is busy, retrying\n", > __func__, pfn_to_page(pfn)); > @@ -420,6 +420,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > start = bitmap_no + mask + 1; > } > > + mutex_unlock(&cma_mutex); > trace_cma_alloc(pfn, page, count, align); > > pr_debug("%s(): returned %p\n", __func__, page); > @@ -445,15 +446,19 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count) > > pr_debug("%s(page %p)\n", __func__, (void *)pages); > > + mutex_lock(&cma_mutex); > pfn = page_to_pfn(pages); > > - if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count) > + if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count) { > + mutex_unlock(&cma_mutex); > return false; > + } > > VM_BUG_ON(pfn + count > cma->base_pfn + cma->count); > > free_contig_range(pfn, count); > cma_clear_bitmap(cma, pfn, count); > + mutex_unlock(&cma_mutex); > trace_cma_release(pfn, pages, count); > > return true; >