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mm: store compound_nr as well as compound_order

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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>
This commit is contained in:
Matthew Wilcox (Oracle)
2020-08-14 17:30:23 -07:00
committed by Linus Torvalds
parent 14a36a4353
commit 1378a5ee45
3 changed files with 8 additions and 3 deletions
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5
include/linux/mm.h
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@@ -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. */