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PTR:; CAT:NONE; SFS:(13230001)(4636009)(366004)(6506007)(36756003)(83380400001)(26005)(186003)(52116002)(7416002)(5660300002)(6916009)(86362001)(6666004)(8936002)(6512007)(2906002)(2616005)(316002)(38350700002)(38100700002)(6486002)(1076003)(66946007)(508600001)(66556008)(66476007)(966005)(8676002)(4326008); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 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 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5d27096f-6d2f-4c54-96b8-08da0692307c X-MS-Exchange-CrossTenant-AuthSource: DB9PR04MB8477.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Mar 2022 14:43:37.9172 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: A7Qgf/x05IPvBdQGYcYiUa1TSSQbA4FKg3Jx6+yQMecfbIHfh1HmSs6srT4O6hyktg4xfUcyWGbK5ulJpuNh1Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR04MB5041 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220315_075838_476986_7D80B5E3 X-CRM114-Status: GOOD ( 12.26 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org We observed an issue with NXP 5.15 LTS kernel that dma_alloc_coherent() may fail sometimes when there're multiple processes trying to allocate CMA memory. This issue can be very easily reproduced on MX6Q SDB board with latest linux-next kernel by writing a test module creating 16 or 32 threads allocating random size of CMA memory in parallel at the background. Or simply enabling CONFIG_CMA_DEBUG, you can see endless of CMA alloc retries during booting: [ 1.452124] cma: cma_alloc(): memory range at (ptrval) is busy,retrying .... (thousands of reties) The root cause of this issue is that since commit a4efc174b382 ("mm/cma.c: remove redundant cma_mutex lock"), CMA supports concurrent memory allocation. It's possible that the memory range process A try to alloc has already been isolated by the allocation of process B during memory migration. The problem here is that the memory range isolated during one allocation by start_isolate_page_range() could be much bigger than the real size we want to alloc due to the range is aligned to MAX_ORDER_NR_PAGES. Taking an ARMv7 platform with 1G memory as an example, when MAX_ORDER_NR_PAGES is big (e.g. 32M with max_order 14) and CMA memory is relatively small (e.g. 128M), there're only 4 MAX_ORDER slot, then it's very easy that all CMA memory may have already been isolated by other processes when one trying to allocate memory using dma_alloc_coherent(). Since current CMA code will only scan one time of whole available CMA memory, then dma_alloc_coherent() may easy fail due to contention with other processes. This patchset introduces a retry mechanism to rescan CMA bitmap for -EBUSY error in case the target pageblock may has been temporarily isolated by others and released later. It also improves the CMA allocation performance by trying the next MAX_ORDER_NR_PAGES range during reties rather than looping within the same isolated range in small steps which wasting CPU mips. The following test is based on linux-next: next-20211213. Without the fix, it's easily fail. # insmod cma_alloc.ko pnum=16 [ 274.322369] CMA alloc test enter: thread number: 16 [ 274.329948] cpu: 0, pid: 692, index 4 pages 144 [ 274.330143] cpu: 1, pid: 694, index 2 pages 44 [ 274.330359] cpu: 2, pid: 695, index 7 pages 757 [ 274.330760] cpu: 2, pid: 696, index 4 pages 144 [ 274.330974] cpu: 2, pid: 697, index 6 pages 512 [ 274.331223] cpu: 2, pid: 698, index 6 pages 512 [ 274.331499] cpu: 2, pid: 699, index 2 pages 44 [ 274.332228] cpu: 2, pid: 700, index 0 pages 7 [ 274.337421] cpu: 0, pid: 701, index 1 pages 38 [ 274.337618] cpu: 2, pid: 702, index 0 pages 7 [ 274.344669] cpu: 1, pid: 703, index 0 pages 7 [ 274.344807] cpu: 3, pid: 704, index 6 pages 512 [ 274.348269] cpu: 2, pid: 705, index 5 pages 148 [ 274.349490] cma: cma_alloc: reserved: alloc failed, req-size: 38 pages, ret: -16 [ 274.366292] cpu: 1, pid: 706, index 4 pages 144 [ 274.366562] cpu: 0, pid: 707, index 3 pages 128 [ 274.367356] cma: cma_alloc: reserved: alloc failed, req-size: 128 pages, ret: -16 [ 274.367370] cpu: 0, pid: 707, index 3 pages 128 failed [ 274.371148] cma: cma_alloc: reserved: alloc failed, req-size: 148 pages, ret: -16 [ 274.375348] cma: cma_alloc: reserved: alloc failed, req-size: 144 pages, ret: -16 [ 274.384256] cpu: 2, pid: 708, index 0 pages 7 .... With the fix, 32 threads allocating in parallel can pass overnight stress test. root@imx6qpdlsolox:~# insmod cma_alloc.ko pnum=32 [ 112.976809] cma_alloc: loading out-of-tree module taints kernel. [ 112.984128] CMA alloc test enter: thread number: 32 [ 112.989748] cpu: 2, pid: 707, index 6 pages 512 [ 112.994342] cpu: 1, pid: 708, index 6 pages 512 [ 112.995162] cpu: 0, pid: 709, index 3 pages 128 [ 112.995867] cpu: 2, pid: 710, index 0 pages 7 [ 112.995910] cpu: 3, pid: 711, index 2 pages 44 [ 112.996005] cpu: 3, pid: 712, index 7 pages 757 [ 112.996098] cpu: 3, pid: 713, index 7 pages 757 ... [41877.368163] cpu: 1, pid: 737, index 2 pages 44 [41877.369388] cpu: 1, pid: 736, index 3 pages 128 [41878.486516] cpu: 0, pid: 737, index 2 pages 44 [41878.486515] cpu: 2, pid: 739, index 4 pages 144 [41878.486622] cpu: 1, pid: 736, index 3 pages 128 [41878.486948] cpu: 2, pid: 735, index 7 pages 757 [41878.487279] cpu: 2, pid: 738, index 4 pages 144 [41879.526603] cpu: 1, pid: 739, index 3 pages 128 [41879.606491] cpu: 2, pid: 737, index 3 pages 128 [41879.606550] cpu: 0, pid: 736, index 0 pages 7 [41879.612271] cpu: 2, pid: 738, index 4 pages 144 ... v1: https://patchwork.kernel.org/project/linux-mm/cover/20211215080242.3034856-1-aisheng.dong@nxp.com/ v2: https://patchwork.kernel.org/project/linux-mm/cover/20220112131552.3329380-1-aisheng.dong@nxp.com/ Dong Aisheng (2): mm: cma: fix allocation may fail sometimes mm: cma: try next MAX_ORDER_NR_PAGES during retry mm/cma.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-)