On Mon, Jun 13, 2022 at 02:35:12PM +0800, Muchun Song wrote:
> -static __init int hugetlb_vmemmap_sysctls_init(void)
> +static int __init hugetlb_vmemmap_init(void)
> {
> + const struct hstate *h;
> + bool optimizable = false;
> +
> /*
> - * If "struct page" crosses page boundaries, the vmemmap pages cannot
> - * be optimized.
> + * There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct
> + * page structs that can be used when HVO is enabled.
> */
> - if (is_power_of_2(sizeof(struct page)))
> - register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
> + BUILD_BUG_ON(__NR_USED_SUBPAGE >= RESERVE_VMEMMAP_SIZE / sizeof(struct page));
I need to take another look, but from the first glance there is something
here that caught my eye.
> +
> + for_each_hstate(h) {
> + char buf[16];
> + unsigned int size = 0;
> +
> + if (hugetlb_vmemmap_optimizable(h))
> + size = hugetlb_vmemmap_size(h) - RESERVE_VMEMMAP_SIZE;
> + optimizable = size ? true : optimizable;
This feels weird, just use false instead of optimizable.
> + string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf,
> + sizeof(buf));
> + pr_info("%d KiB vmemmap can be optimized for a %s page\n",
> + size / SZ_1K, buf);
I do not have a strong opinion but I wonder whether this brings a lot.
--
Oscar Salvador
SUSE Labs
