Re: [RFC] can we use vmalloc to alloc thread stack if compaction failed
From: Michal Hocko <mhocko@kernel.org>
Date: 2016-07-28 07:59:11
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On Thu 28-07-16 15:41:53, Xishi Qiu wrote:
quoted hunk ↗ jump to hunk
On 2016/7/28 15:20, Michal Hocko wrote:quoted
On Thu 28-07-16 15:08:26, Xishi Qiu wrote:quoted
Usually THREAD_SIZE_ORDER is 2, it means we need to alloc 16kb continuous physical memory during fork a new process. If the system's memory is very small, especially the smart phone, maybe there is only 1G memory. So the free memory is very small and compaction is not always success in slowpath(__alloc_pages_slowpath), then alloc thread stack may be failed for memory fragment.Well, with the current implementation of the page allocator those requests will not fail in most cases. The oom killer would be invoked in order to free up some memory.Hi Michal, Yes, it success in most cases, but I did have seen this problem in some stress-test. DMA free:470628kB, but alloc 2 order block failed during fork a new process. There are so many memory fragments and the large block may be soon taken by others after compact because of stress-test.--- dmesg messages ---07-13 08:41:51.341 <4>[309805.658142s][pid:1361,cpu5,sManagerService]sManagerService: page allocation failure: order:2, mode:0x2000d1
Yes but this is __GFP_DMA allocation. I guess you have already reported this failure and you've been told that this is quite unexpected for the kernel stack allocation. It is your out-of-tree patch which just makes things worse because DMA restricted allocations are considered "lowmem" and so they do not invoke OOM killer and do not retry like regular GFP_KERNEL allocations. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>