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It is a rework > of [1] which took a detour through PREEMPT_LAZY [2]. > > Why multi-page clearing?: multi-page clearing improves upon the > current page-at-a-time approach by providing the processor with a > hint as to the real region size. A processor could use this hint to, > for instance, elide cacheline allocation when clearing a large > region. > > This optimization in particular is done by REP; STOS on AMD Zen > where regions larger than L3-size use non-temporal stores. > > This results in significantly better performance. Do you have init_on_alloc=1 in your kernel? With that, pages coming from buddy allocator are zeroed in post_alloc_hook() by kernel_init_pages(), which is a for loop of clear_highpage_kasan_tagged(), a wrap of clear_page(). And folio_zero_user() is not used. At least Debian, Fedora, and Ubuntu by default have CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y, which means init_on_alloc=1. Maybe kernel_init_pages() should get your optimization as well, unless you only target hugetlb pages. Best Regards, Yan, Zi