On 2016/3/3 15:42, Joonsoo Kim wrote: > 2016-03-03 10:25 GMT+09:00 Laura Abbott <labbott@xxxxxxxxxx>: >> (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? 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; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>