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    SubjectRe: [PATCH 6/6] mm: hugetlb_vmemmap: improve hugetlb_vmemmap code readability
    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

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