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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?uVDqTtGOUANcTO/dp3H8OxMAz1D72bIQsYIn2BZIGyda31yQQPh760UtkdqO?= =?us-ascii?Q?2pvk9dp2VZk0UIMMPTh/wS3kVNXa8zAY4b3nzGN5NOr2kIEe+cd27YiDkzGK?= =?us-ascii?Q?VS/pMCQbWlCd+GA+FIZZjkCNbYJhCyeRGmuXFHFwTp/EaTq9PaLxsEBaCBus?= =?us-ascii?Q?naLs7IQgFwZE5KjB5iM+ScgogOoP0eyxwU27k8Ikuo30QAu84OfqC06OJ+YY?= =?us-ascii?Q?h9wzjLGj39UlCtULwxtTvEpbSYEnydE5g8tB1aE22QQ6a6nt4/OLrmboasO1?= =?us-ascii?Q?PZnkQqEpCck/RxiCM6uZj1efgbizVwsTUlbr1/DvhrjNLaXUZDqS9ays0//P?= =?us-ascii?Q?G9N/3IduvksfJoa+zOxpzZMXb5mIieDGx61EjdVcraCE6cL4koo5CJAN4gaJ?= =?us-ascii?Q?QaYGDaCDxuLf1rf3y5McX4x3u4NnLLcUynFazSZmYERUqaPUfSD/7zAZShTV?= =?us-ascii?Q?H+cHDrXAFRsocdnyxDe4f/J7FAnRfvBp5gnm6T2ofTIsZBQmllo+KoUpzEbo?= =?us-ascii?Q?WBmaREWOdPIdDoJ679j5boEz78gnK9W7KldRuUqsaY/OgvfTWv7LiR2y6ERe?= =?us-ascii?Q?g8MSFel10Mv/3HINYS96HQLKggPR5vqMd048YD1UB1ZLQWbTovT33+70++DE?= =?us-ascii?Q?gMpSyfuA86Sku4CH5rIXFsMpJ+PCNNH4/hBboU2AAcg4P/83YJy7/IfFeASN?= =?us-ascii?Q?Itwfi8ewZ1LHPXJ/78VSrsN0PbzDXpMcYKhkqFVxQkqm6ATPSznUDEzPaFgm?= =?us-ascii?Q?Y0NNqRdTohlbNj1BmTXlK184qpayel7TtYeMWIlKT8lsM+vaW8jOmAn6Hz57?= =?us-ascii?Q?0KcSRlFHVtoSW0b8IRPtyvq/DgmCtFpwx0nbqfsCTimG27AGBxB7qwZ2Ukhv?= =?us-ascii?Q?ilnvgBynJ+QhsSxdKTBu8jvRLSSgkCW2z5UJlqhjX57Lr2Vd5Xeccc3osxYA?= =?us-ascii?Q?iUCXV/VeAXBcYy+uExGP94QxQ+Np1bZKFK6dY9QLHGV6EDbvoVhPXGN5x1Lk?= =?us-ascii?Q?ErgNotZLM/Ws6GJvCoDKxqkkeWtwFT1bjFAqrxigKeRG1g8asdtoGDGz7cZL?= =?us-ascii?Q?ARyyLtLG7MzUbIMZI8c8h8M405/GLxpKmoC8lmnPiJAG8RMiXKR15r6MJTpG?= =?us-ascii?Q?ZDHA09Mm4gS6vCytQ2KPY6JDFHd+Wc8B/qWYlSTQEt7RJ51xi14SsMx0FQPY?= =?us-ascii?Q?p/gffeP7MOQWKou7W/bE6VV3HamDZcxfWqE3dbFJ5Ytu9YLFkWXklJ0GHAHN?= =?us-ascii?Q?sdl6cs3rxlUM8fpCVSki6F9Nz8ZDDnCHREkFgv9kn6Q9C2MhHahQmY2HdSQm?= =?us-ascii?Q?ELPJjCAZSMu8Z/KjXfi2D9KwzZqEfYy/vXbtUUHK60p1k0jXmjs/k3sCTRMu?= =?us-ascii?Q?5THk0BiDVJPnNwhnAni33P7+jPyhZd8e7U4XKtEFvXSfAMkXSdAjR4QHu3EW?= =?us-ascii?Q?waB1PFb/6s1gxiSI2WmONbWknzWrp074b5DevMBNb6vtk2acGYGDRndIgkle?= =?us-ascii?Q?wTSkbghMsb4bvCNnDUqwbzxnUlIOpfhSwcOofsSv5kwNzOU+wtiAbPWwdS52?= =?us-ascii?Q?xEYbJOCJKV22SsVNr5NAmAtK6mrYgAKqpMragMC8joW6lZoNvN1frZhwMEYc?= =?us-ascii?Q?QnmKhpl+zAhmgV0bPTyQ8mQ6BjPGK+GzvMiE1X9Ww1/ry2TBJC1ecl61Uf6b?= =?us-ascii?Q?aAoNyQskAOdiZbu20etO21UkNjC3Hc2NCNRIhHHEN+1qil7E?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5fd237ef-a57d-4039-98e6-08de9fac1c69 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Apr 2026 13:44:29.4595 (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: bHIIiLPTNX5ZGqut08DOWZYu0asS/O6fql9nsY9EjPztYmEqEZpKKdEsP4BLuPAO X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ5PPFABE38415D On 21 Apr 2026, at 0:24, Hrushikesh Salunke wrote: > When init_on_alloc is enabled, kernel_init_pages() clears every page > one at a time via clear_highpage_kasan_tagged(), which incurs per-page > kmap_local_page()/kunmap_local() overhead and prevents the architecture > clearing primitive from operating on contiguous ranges. > > Introduce clear_highpages_kasan_tagged() in highmem.h, a batch > clearing helper that calls clear_pages() for the full contiguous range > on !HIGHMEM systems, bypassing the per-page kmap overhead and allowing > a single invocation of the arch clearing primitive across the entire > allocation. The HIGHMEM path falls back to per-page clearing since > those pages require kmap. > > Use it in kernel_init_pages() to replace the per-page loop. > > Allocating 8192 x 2MB HugeTLB pages (16GB) with init_on_alloc=1: > > Before: 0.445s > After: 0.166s (-62.7%, 2.68x faster) > > Kernel time (sys) reduction per workload with init_on_alloc=1: > > Workload Before After Change > Graph500 64C128T 30m 41.8s 15m 14.8s -50.3% > Graph500 16C32T 15m 56.7s 9m 43.7s -39.0% > Pagerank 32T 1m 58.5s 1m 12.8s -38.5% > Pagerank 128T 2m 36.3s 1m 40.4s -35.7% > > Signed-off-by: Hrushikesh Salunke > --- > base commit: f1541b40cd422d7e22273be9b7e9edfc9ea4f0d7 > > v1: https://lore.kernel.org/all/20260408092441.435133-1-hsalunke@amd.com/ > > Changes since v1: > - Dropped cond_resched() and PROCESS_PAGES_NON_PREEMPT_BATCH as > kernel_init_pages() runs inside the page allocator and can be > called from atomic context, making cond_resched() unsafe. The > original code never had a cond_resched() here, and the > performance gain comes from batching, not rescheduling. > > - Moved the !HIGHMEM/HIGHMEM branching into a new > clear_highpages_kasan_tagged() helper in highmem.h, per David's > suggestion. > > include/linux/highmem.h | 12 ++++++++++++ > mm/page_alloc.c | 5 +---- > 2 files changed, 13 insertions(+), 4 deletions(-) > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index af03db851a1d..ad0f42d06ce6 100644 > --- a/include/linux/highmem.h > +++ b/include/linux/highmem.h > @@ -345,6 +345,18 @@ static inline void clear_highpage_kasan_tagged(struct page *page) > kunmap_local(kaddr); > } > > +static inline void clear_highpages_kasan_tagged(struct page *page, int numpages) > +{ > + if (!IS_ENABLED(CONFIG_HIGHMEM)) { > + clear_pages(kasan_reset_tag(page_address(page)), numpages); kasan_reset_tag() here removes the tag from page address, so that clear_pages() can use the right kaddr. I thought each page needs a kasan_reset_tag(). No need to respond here, as I am reading the code and trying to understand how it works. Acked-by: Zi Yan > + } else { > + int i; > + > + for (i = 0; i < numpages; i++) > + clear_highpage_kasan_tagged(page + i); > + } > +} > + > #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGES > > /* Return false to let people know we did not initialize the pages */ > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index b1c5430cad4e..1aaf7f839ff4 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1220,12 +1220,9 @@ static inline bool should_skip_kasan_poison(struct page *page) > > static void kernel_init_pages(struct page *page, int numpages) > { > - int i; > - > /* s390's use of memset() could override KASAN redzones. */ > kasan_disable_current(); > - for (i = 0; i < numpages; i++) > - clear_highpage_kasan_tagged(page + i); > + clear_highpages_kasan_tagged(page, numpages); > kasan_enable_current(); > } > > -- > 2.43.0 Best Regards, Yan, Zi