The patch titled
Subject: mm: incorporate zero pages into transparent huge pages
has been added to the -mm tree. Its filename is
mm-incorporate-zero-pages-into-transparent-huge-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-incorporate-zero-pages-into-transparent-huge-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-incorporate-zero-pages-into-transparent-huge-pages.patch
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From: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Subject: mm: incorporate zero pages into transparent huge pages
This patch improves THP collapse rates, by allowing zero pages.
Currently THP can collapse 4kB pages into a THP when there are up to
khugepaged_max_ptes_none pte_none ptes in a 2MB range. This patch counts
pte none and mapped zero pages with the same variable.
The patch was tested with a program that allocates 800MB of
memory, and performs interleaved reads and writes, in a pattern
that causes some 2MB areas to first see read accesses, resulting
in the zero pfn being mapped there.
To simulate memory fragmentation at allocation time, I modified
do_huge_pmd_anonymous_page to return VM_FAULT_FALLBACK for read faults.
Without the patch, only %50 of the program was collapsed into THP and the
percentage did not increase over time.
With this patch after 10 minutes of waiting khugepaged had collapsed %99
of the program's memory.
Signed-off-by: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff -puN mm/huge_memory.c~mm-incorporate-zero-pages-into-transparent-huge-pages mm/huge_memory.c
--- a/mm/huge_memory.c~mm-incorporate-zero-pages-into-transparent-huge-pages
+++ a/mm/huge_memory.c
@@ -2104,7 +2104,7 @@ static void release_pte_pages(pte_t *pte
{
while (--_pte >= pte) {
pte_t pteval = *_pte;
- if (!pte_none(pteval))
+ if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
release_pte_page(pte_page(pteval));
}
}
@@ -2115,13 +2115,13 @@ static int __collapse_huge_page_isolate(
{
struct page *page;
pte_t *_pte;
- int none = 0;
+ int none_or_zero = 0;
bool referenced = false, writable = false;
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
- if (pte_none(pteval)) {
- if (++none <= khugepaged_max_ptes_none)
+ if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
+ if (++none_or_zero <= khugepaged_max_ptes_none)
continue;
else
goto out;
@@ -2202,7 +2202,7 @@ static void __collapse_huge_page_copy(pt
pte_t pteval = *_pte;
struct page *src_page;
- if (pte_none(pteval)) {
+ if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
clear_user_highpage(page, address);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
} else {
@@ -2538,7 +2538,7 @@ static int khugepaged_scan_pmd(struct mm
{
pmd_t *pmd;
pte_t *pte, *_pte;
- int ret = 0, none = 0;
+ int ret = 0, none_or_zero = 0;
struct page *page;
unsigned long _address;
spinlock_t *ptl;
@@ -2556,8 +2556,8 @@ static int khugepaged_scan_pmd(struct mm
for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, _address += PAGE_SIZE) {
pte_t pteval = *_pte;
- if (pte_none(pteval)) {
- if (++none <= khugepaged_max_ptes_none)
+ if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
+ if (++none_or_zero <= khugepaged_max_ptes_none)
continue;
else
goto out_unmap;
_
Patches currently in -mm which might be from ebru.akagunduz@xxxxxxxxx are
origin.patch
mm-incorporate-zero-pages-into-transparent-huge-pages.patch
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