mm, thp: convert from optimistic swapin collapsing to conservative
To detect whether khugepaged swapin is worthwhile, this patch checks the
amount of young pages. There should be at least half of HPAGE_PMD_NR to
swapin.
Link: http://lkml.kernel.org/r/1468109451-1615-1-git-send-email-ebru.akagunduz@gmail.com
Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5661484..7dbee69 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -27,7 +27,7 @@
SCAN_EXCEED_NONE_PTE,
SCAN_PTE_NON_PRESENT,
SCAN_PAGE_RO,
- SCAN_NO_REFERENCED_PAGE,
+ SCAN_LACK_REFERENCED_PAGE,
SCAN_PAGE_NULL,
SCAN_SCAN_ABORT,
SCAN_PAGE_COUNT,
@@ -500,8 +500,8 @@
{
struct page *page = NULL;
pte_t *_pte;
- int none_or_zero = 0, result = 0;
- bool referenced = false, writable = false;
+ int none_or_zero = 0, result = 0, referenced = 0;
+ bool writable = false;
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
@@ -580,11 +580,11 @@
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageLRU(page), page);
- /* If there is no mapped pte young don't collapse the page */
+ /* There should be enough young pte to collapse the page */
if (pte_young(pteval) ||
page_is_young(page) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
- referenced = true;
+ referenced++;
}
if (likely(writable)) {
if (likely(referenced)) {
@@ -869,7 +869,8 @@
static bool __collapse_huge_page_swapin(struct mm_struct *mm,
struct vm_area_struct *vma,
- unsigned long address, pmd_t *pmd)
+ unsigned long address, pmd_t *pmd,
+ int referenced)
{
pte_t pteval;
int swapped_in = 0, ret = 0;
@@ -887,12 +888,19 @@
if (!is_swap_pte(pteval))
continue;
swapped_in++;
+ /* we only decide to swapin, if there is enough young ptes */
+ if (referenced < HPAGE_PMD_NR/2) {
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
+ return false;
+ }
ret = do_swap_page(&fe, pteval);
+
/* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
if (ret & VM_FAULT_RETRY) {
down_read(&mm->mmap_sem);
if (hugepage_vma_revalidate(mm, address)) {
/* vma is no longer available, don't continue to swapin */
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
}
/* check if the pmd is still valid */
@@ -900,7 +908,7 @@
return false;
}
if (ret & VM_FAULT_ERROR) {
- trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
}
/* pte is unmapped now, we need to map it */
@@ -908,7 +916,7 @@
}
fe.pte--;
pte_unmap(fe.pte);
- trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
return true;
}
@@ -916,7 +924,7 @@
unsigned long address,
struct page **hpage,
struct vm_area_struct *vma,
- int node)
+ int node, int referenced)
{
pmd_t *pmd, _pmd;
pte_t *pte;
@@ -973,7 +981,7 @@
* If it fails, we release mmap_sem and jump out_nolock.
* Continuing to collapse causes inconsistency.
*/
- if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
+ if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
mem_cgroup_cancel_charge(new_page, memcg, true);
up_read(&mm->mmap_sem);
goto out_nolock;
@@ -1084,12 +1092,12 @@
{
pmd_t *pmd;
pte_t *pte, *_pte;
- int ret = 0, none_or_zero = 0, result = 0;
+ int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
struct page *page = NULL;
unsigned long _address;
spinlock_t *ptl;
int node = NUMA_NO_NODE, unmapped = 0;
- bool writable = false, referenced = false;
+ bool writable = false;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
@@ -1177,14 +1185,14 @@
if (pte_young(pteval) ||
page_is_young(page) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
- referenced = true;
+ referenced++;
}
if (writable) {
if (referenced) {
result = SCAN_SUCCEED;
ret = 1;
} else {
- result = SCAN_NO_REFERENCED_PAGE;
+ result = SCAN_LACK_REFERENCED_PAGE;
}
} else {
result = SCAN_PAGE_RO;
@@ -1194,7 +1202,7 @@
if (ret) {
node = khugepaged_find_target_node();
/* collapse_huge_page will return with the mmap_sem released */
- collapse_huge_page(mm, address, hpage, vma, node);
+ collapse_huge_page(mm, address, hpage, vma, node, referenced);
}
out:
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,