The patch titled
SHM_LOCKED pages are unevictable
has been added to the -mm tree. Its filename is
shm_locked-pages-are-unevictable.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
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out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: SHM_LOCKED pages are unevictable
From: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
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. Note that scan_mapping_unevictable_page() must be able to sleep
on page_lock(), so we can't call it holding the shmem info spinlock nor
the shmid spinlock. So, we pass the mapping [address_space] back to
shmctl() on SHM_UNLOCK for rescuing any unevictable pages after dropping
the spinlocks. Once we drop the shmid lock, the backing shmem file can be
deleted if the calling task doesn't have the shm area attached. To handle
this, we take an extra reference on the file before dropping the shmid
lock and drop the reference after scanning the mapping's unevictable
pages.
Changes depend on [CONFIG_]UNEVICTABLE_LRU.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Kosaki Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 9 ++-
include/linux/pagemap.h | 12 +++-
include/linux/swap.h | 4 +
ipc/shm.c | 20 +++++++-
mm/shmem.c | 10 ++--
mm/vmscan.c | 93 ++++++++++++++++++++++++++++++++++++++
6 files changed, 136 insertions(+), 12 deletions(-)
diff -puN include/linux/mm.h~shm_locked-pages-are-unevictable include/linux/mm.h
--- a/include/linux/mm.h~shm_locked-pages-are-unevictable
+++ a/include/linux/mm.h
@@ -701,12 +701,13 @@ static inline int page_mapped(struct pag
extern void show_free_areas(void);
#ifdef CONFIG_SHMEM
-int shmem_lock(struct file *file, int lock, struct user_struct *user);
+extern struct address_space *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)
+static inline struct address_space *shmem_lock(struct file *file, int lock,
+ struct user_struct *user)
{
- return 0;
+ return NULL;
}
#endif
struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags);
diff -puN include/linux/pagemap.h~shm_locked-pages-are-unevictable include/linux/pagemap.h
--- a/include/linux/pagemap.h~shm_locked-pages-are-unevictable
+++ a/include/linux/pagemap.h
@@ -39,14 +39,20 @@ static inline void mapping_set_unevictab
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 -puN include/linux/swap.h~shm_locked-pages-are-unevictable include/linux/swap.h
--- a/include/linux/swap.h~shm_locked-pages-are-unevictable
+++ a/include/linux/swap.h
@@ -232,12 +232,16 @@ static inline int zone_reclaim(struct zo
#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 -puN ipc/shm.c~shm_locked-pages-are-unevictable ipc/shm.c
--- a/ipc/shm.c~shm_locked-pages-are-unevictable
+++ a/ipc/shm.c
@@ -737,6 +737,11 @@ asmlinkage long sys_shmctl(int shmid, in
case SHM_LOCK:
case SHM_UNLOCK:
{
+ struct address_space *mapping = NULL;
+ 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);
@@ -764,18 +769,29 @@ asmlinkage long sys_shmctl(int shmid, in
if(cmd==SHM_LOCK) {
struct user_struct * user = current->user;
if (!is_file_hugepages(shp->shm_file)) {
- err = shmem_lock(shp->shm_file, 1, user);
+ mapping = shmem_lock(shp->shm_file, 1, user);
+ if (IS_ERR(mapping))
+ err = PTR_ERR(mapping);
+ mapping = NULL;
if (!err && !(shp->shm_perm.mode & SHM_LOCKED)){
shp->shm_perm.mode |= SHM_LOCKED;
shp->mlock_user = user;
}
}
} else if (!is_file_hugepages(shp->shm_file)) {
- shmem_lock(shp->shm_file, 0, shp->mlock_user);
+ mapping = shmem_lock(shp->shm_file, 0, shp->mlock_user);
shp->shm_perm.mode &= ~SHM_LOCKED;
shp->mlock_user = NULL;
+ if (mapping) {
+ shm_file = shp->shm_file;
+ get_file(shm_file); /* hold across unlock */
+ }
}
shm_unlock(shp);
+ if (mapping) {
+ scan_mapping_unevictable_pages(mapping);
+ fput(shm_file);
+ }
goto out;
}
case IPC_RMID:
diff -puN mm/shmem.c~shm_locked-pages-are-unevictable mm/shmem.c
--- a/mm/shmem.c~shm_locked-pages-are-unevictable
+++ a/mm/shmem.c
@@ -1473,23 +1473,27 @@ static struct mempolicy *shmem_get_polic
}
#endif
-int shmem_lock(struct file *file, int lock, struct user_struct *user)
+struct address_space *shmem_lock(struct file *file, int lock,
+ struct user_struct *user)
{
struct inode *inode = file->f_path.dentry->d_inode;
struct shmem_inode_info *info = SHMEM_I(inode);
- int retval = -ENOMEM;
+ struct address_space *retval = ERR_PTR(-ENOMEM);
spin_lock(&info->lock);
if (lock && !(info->flags & VM_LOCKED)) {
if (!user_shm_lock(inode->i_size, user))
goto out_nomem;
info->flags |= VM_LOCKED;
+ mapping_set_unevictable(file->f_mapping);
+ retval = NULL;
}
if (!lock && (info->flags & VM_LOCKED) && user) {
user_shm_unlock(inode->i_size, user);
info->flags &= ~VM_LOCKED;
+ mapping_clear_unevictable(file->f_mapping);
+ retval = file->f_mapping;
}
- retval = 0;
out_nomem:
spin_unlock(&info->lock);
return retval;
diff -puN mm/vmscan.c~shm_locked-pages-are-unevictable mm/vmscan.c
--- a/mm/vmscan.c~shm_locked-pages-are-unevictable
+++ a/mm/vmscan.c
@@ -2370,4 +2370,97 @@ int page_evictable(struct page *page, st
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)
+{
+
+ ClearPageUnevictable(page); /* for page_evictable() */
+ 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);
+ } else {
+ /*
+ * rotate unevictable list
+ */
+ SetPageUnevictable(page);
+ list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
+ }
+}
+
+/**
+ * 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;
+
+ 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);
+
+ if (page_index > next)
+ next = page_index;
+ next++;
+
+ if (TestSetPageLocked(page)) {
+ /*
+ * OK, let's do it the hard way...
+ */
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ zone = NULL;
+ lock_page(page);
+ }
+
+ 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);
+
+ unlock_page(page);
+
+ }
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ pagevec_release(&pvec);
+ }
+
+}
#endif
_
Patches currently in -mm which might be from Lee.Schermerhorn@xxxxxx are
vmscan-move-isolate_lru_page-to-vmscanc.patch
vmscan-free-swap-space-on-swap-in-activation.patch
vmscan-split-lru-lists-into-anon-file-sets.patch
unevictable-lru-infrastructure.patch
unevictable-lru-page-statistics.patch
ramfs-and-ram-disk-pages-are-unevictable.patch
shm_locked-pages-are-unevictable.patch
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