In shrink_page_list, call to page_referenced_file will causes the
acquisition/release of mapping->i_mmap_mutex for each page in the page
list. However, it is very likely that successive pages in the list
share the same mapping and we can reduce the frequency of i_mmap_mutex
acquisition by holding the mutex in shrink_page_list. This improves the
performance when the system has a lot page reclamations for file mapped
pages if workloads are using a lot of memory for page cache.
Tim
---
Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
---
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 4b974ae..f0174ae 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -156,8 +156,8 @@ static inline void page_dup_rmap(struct page *page)
/*
* Called from mm/vmscan.c to handle paging out
*/
-int page_referenced(struct page *, int is_locked,
- struct mem_cgroup *memcg, unsigned long *vm_flags);
+int page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg,
+ unsigned long *vm_flags, int mmap_mutex_locked);
int page_referenced_one(struct page *, struct vm_area_struct *,
unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
@@ -175,7 +175,7 @@ enum ttu_flags {
bool is_vma_temporary_stack(struct vm_area_struct *vma);
-int try_to_unmap(struct page *, enum ttu_flags flags, int file_mapped);
+int try_to_unmap(struct page *, enum ttu_flags flags, int mmap_mutex_locked);
int try_to_unmap_one(struct page *, struct vm_area_struct *,
unsigned long address, enum ttu_flags flags);
diff --git a/mm/migrate.c b/mm/migrate.c
index 102a5b1..1aa37b1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -918,7 +918,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
if (PageAnon(hpage))
anon_vma = page_get_anon_vma(hpage);
- try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS, 0);
+ try_to_unmap(hpage,
+ TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS, 0);
if (!page_mapped(hpage))
rc = move_to_new_page(new_hpage, hpage, 1, mode);
diff --git a/mm/rmap.c b/mm/rmap.c
index cb7de48..63fc84b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -820,7 +820,7 @@ static int page_referenced_anon(struct page *page,
*/
static int page_referenced_file(struct page *page,
struct mem_cgroup *memcg,
- unsigned long *vm_flags)
+ unsigned long *vm_flags, int mmap_mutex_locked)
{
unsigned int mapcount;
struct address_space *mapping = page->mapping;
@@ -839,11 +839,14 @@ static int page_referenced_file(struct page *page,
/*
* The page lock not only makes sure that page->mapping cannot
* suddenly be NULLified by truncation, it makes sure that the
- * structure at mapping cannot be freed and reused yet.
- * We should have taken mapping->i_mmap_mutex.
+ * structure at mapping cannot be freed and reused yet,
+ * so we can safely take mapping->i_mmap_mutex.
*/
BUG_ON(!PageLocked(page));
+ if (!mmap_mutex_locked)
+ mutex_lock(&mapping->i_mmap_mutex);
+
/*
* i_mmap_mutex does not stabilize mapcount at all, but mapcount
* is more likely to be accurate if we note it after spinning.
@@ -867,6 +870,8 @@ static int page_referenced_file(struct page *page,
break;
}
+ if (!mmap_mutex_locked)
+ mutex_unlock(&mapping->i_mmap_mutex);
return referenced;
}
@@ -883,7 +888,7 @@ static int page_referenced_file(struct page *page,
int page_referenced(struct page *page,
int is_locked,
struct mem_cgroup *memcg,
- unsigned long *vm_flags)
+ unsigned long *vm_flags, int mmap_mutex_locked)
{
int referenced = 0;
int we_locked = 0;
@@ -903,14 +908,9 @@ int page_referenced(struct page *page,
else if (PageAnon(page))
referenced += page_referenced_anon(page, memcg,
vm_flags);
- else if (page->mapping) {
- if (!is_locked)
- mutex_lock(&page->mapping->i_mmap_mutex);
+ else if (page->mapping)
referenced += page_referenced_file(page, memcg,
- vm_flags);
- if (!is_locked)
- mutex_unlock(&page->mapping->i_mmap_mutex);
- }
+ vm_flags, mmap_mutex_locked);
if (we_locked)
unlock_page(page);
@@ -1550,7 +1550,8 @@ static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
* 'LOCKED.
*/
-static int try_to_unmap_file(struct page *page, enum ttu_flags flags, int filemap_locked)
+static int try_to_unmap_file(struct page *page, enum ttu_flags flags,
+ int mmap_mutex_locked)
{
struct address_space *mapping = page->mapping;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -1562,7 +1563,7 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags, int filema
unsigned long max_nl_size = 0;
unsigned int mapcount;
- if (!filemap_locked)
+ if (!mmap_mutex_locked)
mutex_lock(&mapping->i_mmap_mutex);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
unsigned long address = vma_address(page, vma);
@@ -1643,7 +1644,7 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags, int filema
list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
vma->vm_private_data = NULL;
out:
- if (!filemap_locked)
+ if (!mmap_mutex_locked)
mutex_unlock(&mapping->i_mmap_mutex);
return ret;
}
@@ -1662,7 +1663,7 @@ out:
* SWAP_FAIL - the page is unswappable
* SWAP_MLOCK - page is mlocked.
*/
-int try_to_unmap(struct page *page, enum ttu_flags flags, int filemap_locked)
+int try_to_unmap(struct page *page, enum ttu_flags flags, int mmap_mutex_locked)
{
int ret;
@@ -1674,7 +1675,7 @@ int try_to_unmap(struct page *page, enum ttu_flags flags, int filemap_locked)
else if (PageAnon(page))
ret = try_to_unmap_anon(page, flags);
else
- ret = try_to_unmap_file(page, flags, filemap_locked);
+ ret = try_to_unmap_file(page, flags, mmap_mutex_locked);
if (ret != SWAP_MLOCK && !page_mapped(page))
ret = SWAP_SUCCESS;
return ret;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 83fb7f3..1af1f1c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -27,6 +27,7 @@
buffer_heads_over_limit */
#include <linux/mm_inline.h>
#include <linux/backing-dev.h>
+#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
@@ -781,12 +782,14 @@ enum page_references {
static enum page_references page_check_references(struct page *page,
struct mem_cgroup_zone *mz,
- struct scan_control *sc)
+ struct scan_control *sc,
+ int mmap_mutex_locked)
{
int referenced_ptes, referenced_page;
unsigned long vm_flags;
- referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
+ referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags,
+ mmap_mutex_locked);
referenced_page = TestClearPageReferenced(page);
/* Lumpy reclaim - ignore references */
@@ -856,7 +859,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
unsigned long nr_congested = 0;
unsigned long nr_reclaimed = 0;
unsigned long nr_writeback = 0;
- struct mutex *i_mmap_mutex=NULL;
+ struct mutex *i_mmap_mutex = NULL;
cond_resched();
@@ -866,12 +869,14 @@ static unsigned long shrink_page_list(struct list_head *page_list,
struct address_space *mapping;
struct page *page;
int may_enter_fs;
+ int mmap_mutex_locked;
cond_resched();
page = lru_to_page(page_list);
list_del(&page->lru);
+ mmap_mutex_locked = 0;
if (!trylock_page(page))
goto keep;
@@ -911,15 +916,22 @@ static unsigned long shrink_page_list(struct list_head *page_list,
}
if (page->mapping) {
- if (i_mmap_mutex != &page->mapping->i_mmap_mutex) {
- if (i_mmap_mutex)
- mutex_unlock(i_mmap_mutex);
- i_mmap_mutex = &page->mapping->i_mmap_mutex;
- mutex_lock(i_mmap_mutex);
+ if (i_mmap_mutex == &page->mapping->i_mmap_mutex) {
+ mmap_mutex_locked = 1;
+ } else {
+ if (page_mapped(page) && page_rmapping(page)
+ && !PageKsm(page) && !PageAnon(page)) {
+ if (i_mmap_mutex)
+ mutex_unlock(i_mmap_mutex);
+ i_mmap_mutex = &page->mapping->i_mmap_mutex;
+ mutex_lock(i_mmap_mutex);
+ mmap_mutex_locked = 1;
+ }
}
}
- references = page_check_references(page, mz, sc);
+ references = page_check_references(page, mz, sc,
+ mmap_mutex_locked);
switch (references) {
case PAGEREF_ACTIVATE:
goto activate_locked;
@@ -949,7 +961,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* processes. Try to unmap it here.
*/
if (page_mapped(page) && mapping) {
- switch (try_to_unmap(page, TTU_UNMAP, 1)) {
+ switch (try_to_unmap(page, TTU_UNMAP,
+ mmap_mutex_locked)) {
case SWAP_FAIL:
goto activate_locked;
case SWAP_AGAIN:
@@ -1830,7 +1843,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
}
}
- if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
+ if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags, 0)) {
nr_rotated += hpage_nr_pages(page);
/*
* Identify referenced, file-backed active pages and
--
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