SHM_LOCKED pages are unevictable
Shmem segments locked into memory via shmctl(SHM_LOCKED) should not be
kept on the normal LRU, since scanning them is a waste of time and might
throw off kswapd's balancing algorithms. Place them on the unevictable
LRU list instead.
Use the AS_UNEVICTABLE flag to mark address_space of SHM_LOCKed shared
memory regions as unevictable. Then these pages will be culled off the
normal LRU lists during vmscan.
Add new wrapper function to clear the mapping's unevictable state when/if
shared memory segment is munlocked.
Add 'scan_mapping_unevictable_page()' to mm/vmscan.c to scan all pages in
the shmem segment's mapping [struct address_space] for evictability now
that they're no longer locked. If so, move them to the appropriate zone
lru list.
Changes depend on [CONFIG_]UNEVICTABLE_LRU.
[kosaki.motohiro@jp.fujitsu.com: revert shm change]
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c61ba10..4023629 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -700,10 +700,10 @@
extern void show_free_areas(void);
#ifdef CONFIG_SHMEM
-int shmem_lock(struct file *file, int lock, struct user_struct *user);
+extern int shmem_lock(struct file *file, int lock, struct user_struct *user);
#else
static inline int shmem_lock(struct file *file, int lock,
- struct user_struct *user)
+ struct user_struct *user)
{
return 0;
}
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 09164d2..4b6c4d8 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -40,14 +40,20 @@
set_bit(AS_UNEVICTABLE, &mapping->flags);
}
+static inline void mapping_clear_unevictable(struct address_space *mapping)
+{
+ clear_bit(AS_UNEVICTABLE, &mapping->flags);
+}
+
static inline int mapping_unevictable(struct address_space *mapping)
{
- if (mapping && (mapping->flags & AS_UNEVICTABLE))
- return 1;
- return 0;
+ if (likely(mapping))
+ return test_bit(AS_UNEVICTABLE, &mapping->flags);
+ return !!mapping;
}
#else
static inline void mapping_set_unevictable(struct address_space *mapping) { }
+static inline void mapping_clear_unevictable(struct address_space *mapping) { }
static inline int mapping_unevictable(struct address_space *mapping)
{
return 0;
diff --git a/include/linux/swap.h b/include/linux/swap.h
index a211304..7edb4cb 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -232,12 +232,16 @@
#ifdef CONFIG_UNEVICTABLE_LRU
extern int page_evictable(struct page *page, struct vm_area_struct *vma);
+extern void scan_mapping_unevictable_pages(struct address_space *);
#else
static inline int page_evictable(struct page *page,
struct vm_area_struct *vma)
{
return 1;
}
+static inline void scan_mapping_unevictable_pages(struct address_space *mapping)
+{
+}
#endif
extern int kswapd_run(int nid);
diff --git a/ipc/shm.c b/ipc/shm.c
index e77ec698..0add3fa 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -737,6 +737,10 @@
case SHM_LOCK:
case SHM_UNLOCK:
{
+ struct file *uninitialized_var(shm_file);
+
+ lru_add_drain_all(); /* drain pagevecs to lru lists */
+
shp = shm_lock_check(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
diff --git a/mm/shmem.c b/mm/shmem.c
index fc2ccf7..d38d7e6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1477,12 +1477,16 @@
if (!user_shm_lock(inode->i_size, user))
goto out_nomem;
info->flags |= VM_LOCKED;
+ mapping_set_unevictable(file->f_mapping);
}
if (!lock && (info->flags & VM_LOCKED) && user) {
user_shm_unlock(inode->i_size, user);
info->flags &= ~VM_LOCKED;
+ mapping_clear_unevictable(file->f_mapping);
+ scan_mapping_unevictable_pages(file->f_mapping);
}
retval = 0;
+
out_nomem:
spin_unlock(&info->lock);
return retval;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9babfbc..dfb342e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2346,4 +2346,93 @@
return 1;
}
+
+/**
+ * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
+ * @page: page to check evictability and move to appropriate lru list
+ * @zone: zone page is in
+ *
+ * Checks a page for evictability and moves the page to the appropriate
+ * zone lru list.
+ *
+ * Restrictions: zone->lru_lock must be held, page must be on LRU and must
+ * have PageUnevictable set.
+ */
+static void check_move_unevictable_page(struct page *page, struct zone *zone)
+{
+ VM_BUG_ON(PageActive(page));
+
+retry:
+ ClearPageUnevictable(page);
+ if (page_evictable(page, NULL)) {
+ enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
+ __dec_zone_state(zone, NR_UNEVICTABLE);
+ list_move(&page->lru, &zone->lru[l].list);
+ __inc_zone_state(zone, NR_INACTIVE_ANON + l);
+ __count_vm_event(UNEVICTABLE_PGRESCUED);
+ } else {
+ /*
+ * rotate unevictable list
+ */
+ SetPageUnevictable(page);
+ list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
+ if (page_evictable(page, NULL))
+ goto retry;
+ }
+}
+
+/**
+ * scan_mapping_unevictable_pages - scan an address space for evictable pages
+ * @mapping: struct address_space to scan for evictable pages
+ *
+ * Scan all pages in mapping. Check unevictable pages for
+ * evictability and move them to the appropriate zone lru list.
+ */
+void scan_mapping_unevictable_pages(struct address_space *mapping)
+{
+ pgoff_t next = 0;
+ pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
+ PAGE_CACHE_SHIFT;
+ struct zone *zone;
+ struct pagevec pvec;
+
+ if (mapping->nrpages == 0)
+ return;
+
+ pagevec_init(&pvec, 0);
+ while (next < end &&
+ pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
+ int i;
+ int pg_scanned = 0;
+
+ zone = NULL;
+
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+ pgoff_t page_index = page->index;
+ struct zone *pagezone = page_zone(page);
+
+ pg_scanned++;
+ if (page_index > next)
+ next = page_index;
+ next++;
+
+ if (pagezone != zone) {
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ zone = pagezone;
+ spin_lock_irq(&zone->lru_lock);
+ }
+
+ if (PageLRU(page) && PageUnevictable(page))
+ check_move_unevictable_page(page, zone);
+ }
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ pagevec_release(&pvec);
+
+ count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
+ }
+
+}
#endif