Messages in this thread | | | Date | Thu, 10 Dec 2020 11:25:02 +0100 | From | Oscar Salvador <> | Subject | Re: [PATCH v8 12/12] mm/hugetlb: Optimize the code with the help of the compiler |
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On 2020-12-10 04:55, Muchun Song wrote: > We cannot optimize if a "struct page" crosses page boundaries. If > it is true, we can optimize the code with the help of a compiler. > When free_vmemmap_pages_per_hpage() returns zero, most functions are > optimized by the compiler.
As I said earlier, I would squash this patch with patch#10 and remove the !is_power_of_2 check in hugetlb_vmemmap_init and leave only the check for the boot parameter. That should be enough.
> static inline bool is_hugetlb_free_vmemmap_enabled(void) > { > - return hugetlb_free_vmemmap_enabled; > + return hugetlb_free_vmemmap_enabled && > + is_power_of_2(sizeof(struct page));
Why? hugetlb_free_vmemmap_enabled can only become true if the is_power_of_2 check succeeds in early_hugetlb_free_vmemmap_param. The "is_power_of_2" check here can go.
> diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h > index 0a1c0d33a316..5f5e90c81cd2 100644 > --- a/mm/hugetlb_vmemmap.h > +++ b/mm/hugetlb_vmemmap.h > @@ -21,7 +21,7 @@ void free_huge_page_vmemmap(struct hstate *h, struct > page *head); > */ > static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate > *h) > { > - return h->nr_free_vmemmap_pages; > + return h->nr_free_vmemmap_pages && is_power_of_2(sizeof(struct > page));
If hugetlb_free_vmemmap_enabled is false, hugetlb_vmemmap_init() leaves h->nr_free_vmemmap_pages unset to 0, so no need for the is_power_of_2 check here.
-- Oscar Salvador SUSE L3
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