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Message-Id: <1466594120-2905-3-git-send-email-ebru.akagunduz@gmail.com>
Date: Wed, 22 Jun 2016 14:15:20 +0300
From: Ebru Akagunduz <ebru.akagunduz@...il.com>
To: linux-mm@...ck.org
Cc: hughd@...gle.com, riel@...hat.com, akpm@...ux-foundation.org,
kirill.shutemov@...ux.intel.com, n-horiguchi@...jp.nec.com,
aarcange@...hat.com, iamjoonsoo.kim@....com, gorcunov@...nvz.org,
linux-kernel@...r.kernel.org, mgorman@...e.de, rientjes@...gle.com,
vbabka@...e.cz, aneesh.kumar@...ux.vnet.ibm.com,
hannes@...xchg.org, mhocko@...e.cz, boaz@...xistor.com,
Ebru Akagunduz <ebru.akagunduz@...il.com>
Subject: [RFC PATCH v2 2/3] mm, thp: convert from optimistic swapin collapsing to conservative
To detect whether khugepaged swapin worthwhile, this patch checks
the amount of young pages. There should be at least half of
HPAGE_PMD_NR to swapin.
Signed-off-by: Ebru Akagunduz <ebru.akagunduz@...il.com>
Suggested-by: Minchan Kim <minchan@...nel.org>
---
Changes in v2:
- Don't change thp design, only notice amount of young
pages, if khugepaged needs to swapin (Minchan Kim).
- Print out count of referenced pages in
__collapse_huge_page_swapin() (Ebru Akagunduz)
include/trace/events/huge_memory.h | 19 ++++++++++--------
mm/huge_memory.c | 40 +++++++++++++++++++++++---------------
2 files changed, 35 insertions(+), 24 deletions(-)
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index bda2118..9f69a72 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -13,7 +13,7 @@
EM( SCAN_EXCEED_NONE_PTE, "exceed_none_pte") \
EM( SCAN_PTE_NON_PRESENT, "pte_non_present") \
EM( SCAN_PAGE_RO, "no_writable_page") \
- EM( SCAN_NO_REFERENCED_PAGE, "no_referenced_page") \
+ EM( SCAN_LACK_REFERENCED_PAGE, "lack_referenced_page") \
EM( SCAN_PAGE_NULL, "page_null") \
EM( SCAN_SCAN_ABORT, "scan_aborted") \
EM( SCAN_PAGE_COUNT, "not_suitable_page_count") \
@@ -46,7 +46,7 @@ SCAN_STATUS
TRACE_EVENT(mm_khugepaged_scan_pmd,
TP_PROTO(struct mm_struct *mm, struct page *page, bool writable,
- bool referenced, int none_or_zero, int status, int unmapped),
+ int referenced, int none_or_zero, int status, int unmapped),
TP_ARGS(mm, page, writable, referenced, none_or_zero, status, unmapped),
@@ -54,7 +54,7 @@ TRACE_EVENT(mm_khugepaged_scan_pmd,
__field(struct mm_struct *, mm)
__field(unsigned long, pfn)
__field(bool, writable)
- __field(bool, referenced)
+ __field(int, referenced)
__field(int, none_or_zero)
__field(int, status)
__field(int, unmapped)
@@ -107,14 +107,14 @@ TRACE_EVENT(mm_collapse_huge_page,
TRACE_EVENT(mm_collapse_huge_page_isolate,
TP_PROTO(struct page *page, int none_or_zero,
- bool referenced, bool writable, int status),
+ int referenced, bool writable, int status),
TP_ARGS(page, none_or_zero, referenced, writable, status),
TP_STRUCT__entry(
__field(unsigned long, pfn)
__field(int, none_or_zero)
- __field(bool, referenced)
+ __field(int, referenced)
__field(bool, writable)
__field(int, status)
),
@@ -137,25 +137,28 @@ TRACE_EVENT(mm_collapse_huge_page_isolate,
TRACE_EVENT(mm_collapse_huge_page_swapin,
- TP_PROTO(struct mm_struct *mm, int swapped_in, int ret),
+ TP_PROTO(struct mm_struct *mm, int swapped_in, int referenced, int ret),
- TP_ARGS(mm, swapped_in, ret),
+ TP_ARGS(mm, swapped_in, referenced, ret),
TP_STRUCT__entry(
__field(struct mm_struct *, mm)
__field(int, swapped_in)
+ __field(int, referenced)
__field(int, ret)
),
TP_fast_assign(
__entry->mm = mm;
__entry->swapped_in = swapped_in;
+ __entry->referenced = referenced;
__entry->ret = ret;
),
- TP_printk("mm=%p, swapped_in=%d, ret=%d",
+ TP_printk("mm=%p, swapped_in=%d, referenced=%d, ret=%d",
__entry->mm,
__entry->swapped_in,
+ __entry->referenced,
__entry->ret)
);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 34fec1f..ff96765 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -42,7 +42,7 @@ enum scan_result {
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,
@@ -2048,8 +2048,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
{
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) {
@@ -2128,11 +2128,11 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
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)) {
@@ -2416,7 +2416,8 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address)
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)
{
unsigned long _address;
pte_t *pte, pteval;
@@ -2429,6 +2430,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
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(mm, vma, _address, pte, pmd,
FAULT_FLAG_ALLOW_RETRY,
pteval);
@@ -2436,11 +2442,13 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
if (ret & VM_FAULT_RETRY) {
down_read(&mm->mmap_sem);
/* vma is no longer available, don't continue to swapin */
- if (hugepage_vma_revalidate(mm, address))
+ if (hugepage_vma_revalidate(mm, address)) {
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
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 */
@@ -2448,7 +2456,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
}
pte--;
pte_unmap(pte);
- trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
return true;
}
@@ -2456,7 +2464,7 @@ static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
struct vm_area_struct *vma,
- int node)
+ int node, int referenced)
{
pmd_t *pmd, _pmd;
pte_t *pte;
@@ -2507,7 +2515,7 @@ static void collapse_huge_page(struct mm_struct *mm,
* locked. If it fails, release mmap_sem and jump directly
* out. 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;
@@ -2615,12 +2623,12 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
{
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);
@@ -2708,14 +2716,14 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
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;
@@ -2725,7 +2733,7 @@ out_unmap:
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,
--
1.9.1
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