mm/swap: free swap slots in batch
Add new functions that free unused swap slots in batches without the
need to reacquire swap info lock. This improves scalability and reduce
lock contention.
Link: http://lkml.kernel.org/r/c25e0fcdfd237ec4ca7db91631d3b9f6ed23824e.1484082593.git.tim.c.chen@linux.intel.com
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net> escreveu:
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index e73b544..8b5bd34 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -942,35 +942,34 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
return p;
}
-static unsigned char swap_entry_free(struct swap_info_struct *p,
- swp_entry_t entry, unsigned char usage,
- bool swap_info_locked)
+static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
+ struct swap_info_struct *q)
+{
+ struct swap_info_struct *p;
+
+ p = _swap_info_get(entry);
+
+ if (p != q) {
+ if (q != NULL)
+ spin_unlock(&q->lock);
+ if (p != NULL)
+ spin_lock(&p->lock);
+ }
+ return p;
+}
+
+static unsigned char __swap_entry_free(struct swap_info_struct *p,
+ swp_entry_t entry, unsigned char usage)
{
struct swap_cluster_info *ci;
unsigned long offset = swp_offset(entry);
unsigned char count;
unsigned char has_cache;
- bool lock_swap_info = false;
- if (!swap_info_locked) {
- count = p->swap_map[offset];
- if (!p->cluster_info || count == usage || count == SWAP_MAP_SHMEM) {
-lock_swap_info:
- swap_info_locked = true;
- lock_swap_info = true;
- spin_lock(&p->lock);
- }
- }
-
- ci = lock_cluster(p, offset);
+ ci = lock_cluster_or_swap_info(p, offset);
count = p->swap_map[offset];
- if (!swap_info_locked && (count == usage || count == SWAP_MAP_SHMEM)) {
- unlock_cluster(ci);
- goto lock_swap_info;
- }
-
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
@@ -994,48 +993,54 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
}
usage = count | has_cache;
- p->swap_map[offset] = usage;
+ p->swap_map[offset] = usage ? : SWAP_HAS_CACHE;
- unlock_cluster(ci);
-
- /* free if no reference */
- if (!usage) {
- VM_BUG_ON(!swap_info_locked);
- mem_cgroup_uncharge_swap(entry);
- ci = lock_cluster(p, offset);
- dec_cluster_info_page(p, p->cluster_info, offset);
- unlock_cluster(ci);
- if (offset < p->lowest_bit)
- p->lowest_bit = offset;
- if (offset > p->highest_bit) {
- bool was_full = !p->highest_bit;
- p->highest_bit = offset;
- if (was_full && (p->flags & SWP_WRITEOK)) {
- spin_lock(&swap_avail_lock);
- WARN_ON(!plist_node_empty(&p->avail_list));
- if (plist_node_empty(&p->avail_list))
- plist_add(&p->avail_list,
- &swap_avail_head);
- spin_unlock(&swap_avail_lock);
- }
- }
- atomic_long_inc(&nr_swap_pages);
- p->inuse_pages--;
- frontswap_invalidate_page(p->type, offset);
- if (p->flags & SWP_BLKDEV) {
- struct gendisk *disk = p->bdev->bd_disk;
- if (disk->fops->swap_slot_free_notify)
- disk->fops->swap_slot_free_notify(p->bdev,
- offset);
- }
- }
-
- if (lock_swap_info)
- spin_unlock(&p->lock);
+ unlock_cluster_or_swap_info(p, ci);
return usage;
}
+static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
+{
+ struct swap_cluster_info *ci;
+ unsigned long offset = swp_offset(entry);
+ unsigned char count;
+
+ ci = lock_cluster(p, offset);
+ count = p->swap_map[offset];
+ VM_BUG_ON(count != SWAP_HAS_CACHE);
+ p->swap_map[offset] = 0;
+ dec_cluster_info_page(p, p->cluster_info, offset);
+ unlock_cluster(ci);
+
+ mem_cgroup_uncharge_swap(entry);
+ if (offset < p->lowest_bit)
+ p->lowest_bit = offset;
+ if (offset > p->highest_bit) {
+ bool was_full = !p->highest_bit;
+
+ p->highest_bit = offset;
+ if (was_full && (p->flags & SWP_WRITEOK)) {
+ spin_lock(&swap_avail_lock);
+ WARN_ON(!plist_node_empty(&p->avail_list));
+ if (plist_node_empty(&p->avail_list))
+ plist_add(&p->avail_list,
+ &swap_avail_head);
+ spin_unlock(&swap_avail_lock);
+ }
+ }
+ atomic_long_inc(&nr_swap_pages);
+ p->inuse_pages--;
+ frontswap_invalidate_page(p->type, offset);
+ if (p->flags & SWP_BLKDEV) {
+ struct gendisk *disk = p->bdev->bd_disk;
+
+ if (disk->fops->swap_slot_free_notify)
+ disk->fops->swap_slot_free_notify(p->bdev,
+ offset);
+ }
+}
+
/*
* Caller has made sure that the swap device corresponding to entry
* is still around or has not been recycled.
@@ -1045,8 +1050,10 @@ void swap_free(swp_entry_t entry)
struct swap_info_struct *p;
p = _swap_info_get(entry);
- if (p)
- swap_entry_free(p, entry, 1, false);
+ if (p) {
+ if (!__swap_entry_free(p, entry, 1))
+ swapcache_free_entries(&entry, 1);
+ }
}
/*
@@ -1057,8 +1064,32 @@ void swapcache_free(swp_entry_t entry)
struct swap_info_struct *p;
p = _swap_info_get(entry);
+ if (p) {
+ if (!__swap_entry_free(p, entry, SWAP_HAS_CACHE))
+ swapcache_free_entries(&entry, 1);
+ }
+}
+
+void swapcache_free_entries(swp_entry_t *entries, int n)
+{
+ struct swap_info_struct *p, *prev;
+ int i;
+
+ if (n <= 0)
+ return;
+
+ prev = NULL;
+ p = NULL;
+ for (i = 0; i < n; ++i) {
+ p = swap_info_get_cont(entries[i], prev);
+ if (p)
+ swap_entry_free(p, entries[i]);
+ else
+ break;
+ prev = p;
+ }
if (p)
- swap_entry_free(p, entry, SWAP_HAS_CACHE, false);
+ spin_unlock(&p->lock);
}
/*
@@ -1241,21 +1272,23 @@ int free_swap_and_cache(swp_entry_t entry)
{
struct swap_info_struct *p;
struct page *page = NULL;
+ unsigned char count;
if (non_swap_entry(entry))
return 1;
- p = swap_info_get(entry);
+ p = _swap_info_get(entry);
if (p) {
- if (swap_entry_free(p, entry, 1, true) == SWAP_HAS_CACHE) {
+ count = __swap_entry_free(p, entry, 1);
+ if (count == SWAP_HAS_CACHE) {
page = find_get_page(swap_address_space(entry),
swp_offset(entry));
if (page && !trylock_page(page)) {
put_page(page);
page = NULL;
}
- }
- spin_unlock(&p->lock);
+ } else if (!count)
+ swapcache_free_entries(&entry, 1);
}
if (page) {
/*