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rmap: support file thp

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Naive approach: on mapping/unmapping the page as compound we update
->_mapcount on each 4k page.  That's not efficient, but it's not obvious
how we can optimize this.  We can look into optimization later.

PG_double_map optimization doesn't work for file pages since lifecycle
of file pages is different comparing to anon pages: file page can be
mapped again at any time.

Link: http://lkml.kernel.org/r/1466021202-61880-11-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2016-07-26 15:25:26 -07:00 • committed by Linus Torvalds
parent 7267ec008b
commit dd78fedde4
6 changed files with 52 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

48
mm/rmap.c
View file

@ -1270,18 +1270,34 @@ void page_add_new_anon_rmap(struct page *page,
*
* The caller needs to hold the pte lock.
*/
void page_add_file_rmap(struct page *page)
void page_add_file_rmap(struct page *page, bool compound)
{
int i, nr = 1;
VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
lock_page_memcg(page);
if (atomic_inc_and_test(&page->_mapcount)) {
__inc_zone_page_state(page, NR_FILE_MAPPED);
mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
if (compound && PageTransHuge(page)) {
for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
if (atomic_inc_and_test(&page[i]._mapcount))
nr++;
}
if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
goto out;
} else {
if (!atomic_inc_and_test(&page->_mapcount))
goto out;
}
__mod_zone_page_state(page_zone(page), NR_FILE_MAPPED, nr);
mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
out:
unlock_page_memcg(page);
}
static void page_remove_file_rmap(struct page *page)
static void page_remove_file_rmap(struct page *page, bool compound)
{
int i, nr = 1;
VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
lock_page_memcg(page);
/* Hugepages are not counted in NR_FILE_MAPPED for now. */
@ -1292,15 +1308,24 @@ static void page_remove_file_rmap(struct page *page)
}
/* page still mapped by someone else? */
if (!atomic_add_negative(-1, &page->_mapcount))
goto out;
if (compound && PageTransHuge(page)) {
for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
if (atomic_add_negative(-1, &page[i]._mapcount))
nr++;
}
if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
goto out;
} else {
if (!atomic_add_negative(-1, &page->_mapcount))
goto out;
}
/*
* We use the irq-unsafe __{inc|mod}_zone_page_stat because
* these counters are not modified in interrupt context, and
* pte lock(a spinlock) is held, which implies preemption disabled.
*/
__dec_zone_page_state(page, NR_FILE_MAPPED);
__mod_zone_page_state(page_zone(page), NR_FILE_MAPPED, -nr);
mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
if (unlikely(PageMlocked(page)))
@ -1356,11 +1381,8 @@ static void page_remove_anon_compound_rmap(struct page *page)
*/
void page_remove_rmap(struct page *page, bool compound)
{
if (!PageAnon(page)) {
VM_BUG_ON_PAGE(compound && !PageHuge(page), page);
page_remove_file_rmap(page);
return;
}
if (!PageAnon(page))
return page_remove_file_rmap(page, compound);
if (compound)
return page_remove_anon_compound_rmap(page);