The patch titled
Subject: mm: store compound_nr as well as compound_order
has been added to the -mm tree. Its filename is
mm-store-compound_nr-as-well-as-compound_order.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-store-compound_nr-as-well-as-compound_order.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-store-compound_nr-as-well-as-compound_order.patch
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: store compound_nr as well as compound_order
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.
Link: http://lkml.kernel.org/r/20200629151959.15779-1-willy@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20200629151959.15779-2-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 5 ++++-
include/linux/mm_types.h | 1 +
mm/page_alloc.c | 5 +++--
3 files changed, 8 insertions(+), 3 deletions(-)
--- a/include/linux/mm.h~mm-store-compound_nr-as-well-as-compound_order
+++ a/include/linux/mm.h
@@ -913,12 +913,15 @@ static inline int compound_pincount(stru
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. */
--- a/include/linux/mm_types.h~mm-store-compound_nr-as-well-as-compound_order
+++ a/include/linux/mm_types.h
@@ -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 */
--- a/mm/page_alloc.c~mm-store-compound_nr-as-well-as-compound_order
+++ a/mm/page_alloc.c
@@ -668,8 +668,6 @@ void prep_compound_page(struct page *pag
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;
@@ -677,6 +675,9 @@ void prep_compound_page(struct page *pag
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);
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
vmalloc-convert-to-xarray.patch
mm-store-compound_nr-as-well-as-compound_order.patch
mm-move-page-flags-include-to-top-of-file.patch
mm-add-thp_order.patch
mm-add-thp_size.patch
mm-replace-hpage_nr_pages-with-thp_nr_pages.patch
mm-add-thp_head.patch
mm-introduce-offset_in_thp.patch
