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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?RPWACbVI09PQtTEIAwcYnFLCnf30Dr0XRTSxFXOA0fVIUKxc137EJkXBKAE8?= =?us-ascii?Q?UUXHXyGpP3EmfufDU778jRfuS8Xxlm01ZWaOW2TriOaZyrI+oAeSaHt8XfWs?= =?us-ascii?Q?e7YuNH2vQhoEpAQZAjkaxkLB6LzLfgjLq9CjeFn13x6rRWR29mKRZ7C5zZxA?= =?us-ascii?Q?5TTv1VpMJe1lPVOoyH+jy3Awb/mNc6m428jKGBlFkmyc8TZd3yrZZhxMhTSU?= =?us-ascii?Q?wQnZDp+4yAvr6Wxyxn3DVr/6RuQ3xu40h6N6VwF3XYPaw63bu7IdFM4HuFpX?= =?us-ascii?Q?oDdV66SfY+VPcjkwhb/6r43zgRS4Bf1Sn+RspQri1njTfknU877MYgWYTe5N?= =?us-ascii?Q?dhGdd/0bQwce2VB6j72xX7NNUueJEyyp3AtKWl+errgsRyj0QQLU/zm6JGLg?= =?us-ascii?Q?1urL5f2Ca5Lm5jHZIDe9LFbX/1r0iR9W7Ipng0M+48DlKDBW0YaENkBDnoWM?= =?us-ascii?Q?7NGKP+Vltx1+I58ZJjpem0I0ORUgBOlEzXrz7zmjP7S7A2+uK+b+1aEosMxw?= =?us-ascii?Q?jmuQ89sBFir2rYBgVYjiPQn2400uVZgvdXAOvSP9kFXwXVvNsfaAwvsrJg5n?= =?us-ascii?Q?4fshBd5y1wpRrc8SrIb2tcY4B55r+XpC39kMoSq6YhCeERDUbihFBqUgG74v?= =?us-ascii?Q?O+ZUpsOCb91zvpA1eNjcB/vEjqhOAqTPVxaIk2lDI0ZKAbP8obeZ3/UtRndY?= =?us-ascii?Q?fB6NrYCsm5UVt8hAHF7RT5GutZ3TlhZ1PqUCJ0RxOA6jgCccozk/iMHWenA4?= =?us-ascii?Q?HYkNn8+nCq0y9Td7TorrwBVUCdPPrLoioY/3mWZUQhKI1DyGnrZVRiXwcVZL?= =?us-ascii?Q?Xx2sktu2kyKCLlZ0DmIXi2RNPzDCWBunqDxQr/1LY9Wfejeg+XReCppztSGk?= =?us-ascii?Q?Y4iBDhUsQLkKCMDalAEbsSS9eiyLYhxXHEENwNNjal9mqD8D0Lppx7yJ36u5?= =?us-ascii?Q?TgodNxqbhpndRFCHPoYAD65KCsBp57ofuXe/CKolvoAr/5w+sHwGrcKw/oHd?= =?us-ascii?Q?KBKFtqNS8rYXcRWprMKAP9RZKw4/V0SvTW6/IcVPZ6o2t+UiJDTBGr3KB4Sw?= =?us-ascii?Q?pOThU7SvhuPUbmJjxSAIVcoKFMxXhQUw3Lpmygyhn2zJfMGRdMLAnXQA+b0z?= =?us-ascii?Q?+vdYykabFYv01MgsLvDRx+Jv7prhlQ5zs4xoR63WiWO84SBpR3TvsEe0QZCC?= =?us-ascii?Q?aHSkhhkqjZRlXRDU6WLlh0gHE5Uhc8WDBDBUzAdMR2Eh0nYTd+S4XO/d+VDl?= =?us-ascii?Q?OjThukn1cAHf2DsIdHoHmgoVplzRJycwn7YPdBcm6gZEJurEUtzSCRKu3o1x?= =?us-ascii?Q?/qTmplrynRxiJq+SlDWMAAGNfaJ/p+/E7ZFFiUSjaKPrfvKVePMGpcv89rql?= =?us-ascii?Q?yO/LKmYjnWsPlsF9Slcvu8Tv4NDM4IfswrCv45LqtHdXM/GFuBEBgLGLN/hM?= =?us-ascii?Q?O3wxSAeXCGj68CFRFuoBgoiDEiZydqizOBeho7I7WY8YLaBOPS7fK68K33xW?= =?us-ascii?Q?JDRoKcxe1sw7GVqixh6sw56XX0ITw9k71lrgrqPQxCn7jI/vxHRPE5X7Y+1a?= =?us-ascii?Q?toQopqvmSHCULdPJOVqNsGHdTfzoB8VpoYhOrhHxhTsc+WP0NvGU86W0R8cV?= =?us-ascii?Q?ONGd92sGaU19Oyh7tcbhgRw1Dz8MQXxJQ+H1XRz5fcD9jgM9G5QH71VuR5TV?= =?us-ascii?Q?E6/g38zfK17UuWPbZuJorD7ai9mwZmqotMg8xfyKlMoYcbMr?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3e35f232-18da-4c3d-2db6-08df101a8771 X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Sep 2026 15:37:03.9296 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: gRwPIJmDLfUvZfqsCunUrqu9Bz3anX2cb2qox1xUgTBYNNQAMNEoLHf4qlvh8Dfx X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB4040 On 11 Sep 2026, at 10:21, Salvatore Dipietro wrote: > Commit 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") > introduced high-order folio allocations in the iomap buffered write > path. When memory is fragmented, each failed costly-order allocation > enters __alloc_pages_slowpath() which runs direct compaction and > drain_all_pages(), causing a 0.38x throughput drop on PostgreSQL > pgbench (simple-update) with 1024 clients on a 96-vCPU arm64 system. > > The root issue is that direct compaction is too expensive for hot > allocation paths that have fallbacks to smaller allocations. > __filemap_get_folio_mpol() already marks higher-order allocations with > __GFP_NORETRY | __GFP_NOWARN, signalling that the caller can handle > failure. However, the page allocator still attempts full direct > compaction for costly orders with __GFP_NORETRY, which is unnecessarily= > aggressive when the caller will simply retry at a lower order. > > For costly-order allocations with __GFP_NORETRY, suppress direct reclai= m > for the whole slowpath by computing can_direct_reclaim (and hence > can_compact) as false. The !can_direct_reclaim check near the top of > the slowpath then short-circuits to nopage: no direct reclaim, no direc= t > compaction and no drain_all_pages() IPI across every CPU. kswapd (and > in turn kcompactd) is still woken further down for background > defragmentation, so compaction keeps working for long-term system healt= h > while being removed from the latency-critical direct allocation path. > > Allocations that also request __GFP_THISNODE are exempted. That flag > pairing identifies the local-node-first THP attempt issued by > alloc_pages_mpol() (mempolicy.c), which relies on direct compaction to > form transparent huge pages. __GFP_NOFAIL is exempted as well, so a > must-not-fail allocation is never made to fail. > > Test environment: > Hardware: AWS EC2 m8g.24xlarge (96 vCPU, arm64) > 12x 1TB IO2 32000 IOPS RAID0 XFS > OS: AL2023 > Kernel: v7.3-rc1 > Database: PostgreSQL 18.4 > Workload: pgbench simple-update, 1024 clients, 96 threads, 1200s > > Results (average of 3 runs, TPS): > Config Avg TPS % vs baseline > AL2023 stock 6.1 kernel (pre-5d8edfb900d5) 136,942 n/a > v7.3-rc1 baseline (no patch) 59,408 - > v7.3-rc1 + this patch 161,994 +172.7% > > The patch fully recovers the pre-5d8edfb900d5 performance, bringing > throughput back above the pre-regression level and well clear of the > ~59k baseline. The AL2023 6.1 row runs a kernel that predates commit > 5d8edfb900d5 ("iomap: Copy larger chunks from userspace"), so it is not= > directly comparable, but it shows the pre-regression level and confirms= > that the ~59k baseline is the anomaly and not the norm. > > > Link: https://lore.kernel.org/all/20260403193535.9970-1-dipiets@amazon.= it/T/#t [v1] > Link: https://lore.kernel.org/linux-mm/20260420161404.642-1-dipiets@ama= zon.it/T/#u [v2] > Link: https://lore.kernel.org/all/20260710143437.12379-1-dipiets@amazon= =2Eit/T/#u [v3] > Link: https://lore.kernel.org/all/20260904115629.3993331-1-dipiets@amaz= on.it/T/#u [v4] > Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") > Cc: stable@vger.kernel.org > Cc: Andrew Morton > Cc: Vlastimil Babka > Cc: David Hildenbrand > Cc: Michal Hocko > Cc: Johannes Weiner > Cc: Matthew Wilcox > Cc: Christoph Hellwig > Cc: Dave Chinner > Cc: Ritesh Harjani > Cc: Zi Yan > Cc: linux-mm@kvack.org > Cc: linux-fsdevel@vger.kernel.org > Cc: linux-xfs@vger.kernel.org > Signed-off-by: Salvatore Dipietro > --- > v5: Derive the decision into a local flag instead of mutating gfp_mask > v4: Clear __GFP_DIRECT_RECLAIM early in the slowpath and exempt > __GFP_THISNODE so THP attempt keeps using direct compaction > v3: Move to mm/page_alloc.c, wake kcompactd instead of avoiding it > v2: Move from fs/iomap/buffered-io.c to mm/filemap.c > v1: Avoid compaction in iomap folio allocation > LGTM. Acked-by: Zi Yan Best Regards, Yan, Zi