mm: store compound_nr as well as compound_order (1378a5ee) · Commits · 戴 / test

Patch series "THP prep patches". These are some generic cleanups and improvements, which I would like merged into mmotm soon. The first one should be a performance improvement for all users of compound pages, and the others are aimed at getting code to compile away when CONFIG_TRANSPARENT_HUGEPAGE is disabled (ie small systems). Also better documented / less confusing than the current prefix mixture of compound, hpage and thp. This patch (of 7): This removes a few instructions from functions which need to know how many pages are in a compound page. The storage used is either page->mapping on 64-bit or page->index on 32-bit. Both of these are fine to overlay on tail pages. Signed-off-by:

Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Reviewed-by:

William Kucharski <william.kucharski@oracle.com> Reviewed-by:

Zi Yan <ziy@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Link: http://lkml.kernel.org/r/20200629151959.15779-1-willy@infradead.org Link: http://lkml.kernel.org/r/20200629151959.15779-2-willy@infradead.org Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

+4 −1

Original line number	Diff line number	Diff line
		@@ -922,12 +922,15 @@ static inline int compound_pincount(struct page *page)
		static inline void set_compound_order(struct page *page, unsigned int order)
		{
		page[1].compound_order = order;
		page[1].compound_nr = 1U << order;
		}

		/* Returns the number of pages in this potentially compound page. */
		static inline unsigned long compound_nr(struct page *page)
		{
		return 1UL << compound_order(page);
		if (!PageHead(page))
		return 1;
		return page[1].compound_nr;
		}

		/* Returns the number of bytes in this potentially compound page. */

include/linux/mm_types.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -134,6 +134,7 @@ struct page {
		unsigned char compound_dtor;
		unsigned char compound_order;
		atomic_t compound_mapcount;
		unsigned int compound_nr; /* 1 << compound_order */
		};
		struct { /* Second tail page of compound page */
		unsigned long _compound_pad_1; /* compound_head */

mm/page_alloc.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -666,8 +666,6 @@ void prep_compound_page(struct page *page, unsigned int order)
		int i;
		int nr_pages = 1 << order;

		set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
		set_compound_order(page, order);
		__SetPageHead(page);
		for (i = 1; i < nr_pages; i++) {
		struct page *p = page + i;
		@@ -675,6 +673,9 @@ void prep_compound_page(struct page *page, unsigned int order)
		p->mapping = TAIL_MAPPING;
		set_compound_head(p, page);
		}

		set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
		set_compound_order(page, order);
		atomic_set(compound_mapcount_ptr(page), -1);
		if (hpage_pincount_available(page))
		atomic_set(compound_pincount_ptr(page), 0);

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