[PATCH v3 3/3] vfs: Use per-cpu list for superblock's inode list
From: Waiman Long
Date: Tue Feb 23 2016 - 14:06:26 EST
When many threads are trying to add or delete inode to or from
a superblock's s_inodes list, spinlock contention on the list can
become a performance bottleneck.
This patch changes the s_inodes field to become a per-cpu list with
per-cpu spinlocks. As a result, the following superblock inode list
(sb->s_inodes) iteration functions in vfs are also being modified:
1. iterate_bdevs()
2. drop_pagecache_sb()
3. wait_sb_inodes()
4. evict_inodes()
5. invalidate_inodes()
6. fsnotify_unmount_inodes()
7. add_dquot_ref()
8. remove_dquot_ref()
With an exit microbenchmark that creates a large number of threads,
attachs many inodes to them and then exits. The runtimes of that
microbenchmark with 1000 threads before and after the patch on a
4-socket Intel E7-4820 v3 system (40 cores, 80 threads) were as
follows:
Kernel Elapsed Time System Time
------ ------------ -----------
Vanilla 4.5-rc4 65.29s 82m14s
Patched 4.5-rc4 22.81s 23m03s
Before the patch, spinlock contention at the inode_sb_list_add()
function at the startup phase and the inode_sb_list_del() function at
the exit phase were about 79% and 93% of total CPU time respectively
(as measured by perf). After the patch, the percpu_list_add()
function consumed only about 0.04% of CPU time at startup phase. The
percpu_list_del() function consumed about 0.4% of CPU time at exit
phase. There were still some spinlock contention, but they happened
elsewhere.
Signed-off-by: Waiman Long <Waiman.Long@xxxxxxx>
---
fs/block_dev.c | 13 +++++++------
fs/drop_caches.c | 10 +++++-----
fs/fs-writeback.c | 13 +++++++------
fs/inode.c | 40 +++++++++++++++++-----------------------
fs/notify/inode_mark.c | 10 +++++-----
fs/quota/dquot.c | 16 ++++++++--------
fs/super.c | 7 ++++---
include/linux/fs.h | 8 ++++----
8 files changed, 57 insertions(+), 60 deletions(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 39b3a17..759d9b6 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1865,11 +1865,13 @@ EXPORT_SYMBOL(__invalidate_device);
void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
{
struct inode *inode, *old_inode = NULL;
+ DEFINE_PCPU_LIST_STATE(state);
- spin_lock(&blockdev_superblock->s_inode_list_lock);
- list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
- struct address_space *mapping = inode->i_mapping;
+ while (pcpu_list_iterate(blockdev_superblock->s_inodes, &state)) {
+ struct address_space *mapping;
+ inode = list_entry(state.curr, struct inode, i_sb_list);
+ mapping = inode->i_mapping;
spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
mapping->nrpages == 0) {
@@ -1878,7 +1880,7 @@ void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
+ spin_unlock(state.lock);
/*
* We hold a reference to 'inode' so it couldn't have been
* removed from s_inodes list while we dropped the
@@ -1892,8 +1894,7 @@ void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
func(I_BDEV(inode), arg);
- spin_lock(&blockdev_superblock->s_inode_list_lock);
+ spin_lock(state.lock);
}
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
iput(old_inode);
}
diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index d72d52b..ec272ed 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -16,9 +16,10 @@ int sysctl_drop_caches;
static void drop_pagecache_sb(struct super_block *sb, void *unused)
{
struct inode *inode, *toput_inode = NULL;
+ DEFINE_PCPU_LIST_STATE(state);
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ while (pcpu_list_iterate(sb->s_inodes, &state)) {
+ inode = list_entry(state.curr, struct inode, i_sb_list);
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
(inode->i_mapping->nrpages == 0)) {
@@ -27,15 +28,14 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ spin_unlock(state.lock);
invalidate_mapping_pages(inode->i_mapping, 0, -1);
iput(toput_inode);
toput_inode = inode;
- spin_lock(&sb->s_inode_list_lock);
+ spin_lock(state.lock);
}
- spin_unlock(&sb->s_inode_list_lock);
iput(toput_inode);
}
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 6915c95..05b3f85 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2107,6 +2107,7 @@ EXPORT_SYMBOL(__mark_inode_dirty);
static void wait_sb_inodes(struct super_block *sb)
{
struct inode *inode, *old_inode = NULL;
+ DEFINE_PCPU_LIST_STATE(state);
/*
* We need to be protected against the filesystem going from
@@ -2115,7 +2116,6 @@ static void wait_sb_inodes(struct super_block *sb)
WARN_ON(!rwsem_is_locked(&sb->s_umount));
mutex_lock(&sb->s_sync_lock);
- spin_lock(&sb->s_inode_list_lock);
/*
* Data integrity sync. Must wait for all pages under writeback,
@@ -2124,9 +2124,11 @@ static void wait_sb_inodes(struct super_block *sb)
* In which case, the inode may not be on the dirty list, but
* we still have to wait for that writeout.
*/
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
- struct address_space *mapping = inode->i_mapping;
+ while (pcpu_list_iterate(sb->s_inodes, &state)) {
+ struct address_space *mapping;
+ inode = list_entry(state.curr, struct inode, i_sb_list);
+ mapping = inode->i_mapping;
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
(mapping->nrpages == 0)) {
@@ -2135,7 +2137,7 @@ static void wait_sb_inodes(struct super_block *sb)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ spin_unlock(state.lock);
/*
* We hold a reference to 'inode' so it couldn't have been
@@ -2157,9 +2159,8 @@ static void wait_sb_inodes(struct super_block *sb)
cond_resched();
- spin_lock(&sb->s_inode_list_lock);
+ spin_lock(state.lock);
}
- spin_unlock(&sb->s_inode_list_lock);
iput(old_inode);
mutex_unlock(&sb->s_sync_lock);
}
diff --git a/fs/inode.c b/fs/inode.c
index 9f62db3..e6e41ef 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -28,7 +28,7 @@
* inode->i_state, inode->i_hash, __iget()
* Inode LRU list locks protect:
* inode->i_sb->s_inode_lru, inode->i_lru
- * inode->i_sb->s_inode_list_lock protects:
+ * inode->i_sb->s_inodes->lock protects:
* inode->i_sb->s_inodes, inode->i_sb_list
* bdi->wb.list_lock protects:
* bdi->wb.b_{dirty,io,more_io,dirty_time}, inode->i_io_list
@@ -37,7 +37,7 @@
*
* Lock ordering:
*
- * inode->i_sb->s_inode_list_lock
+ * inode->i_sb->s_inodes->lock
* inode->i_lock
* Inode LRU list locks
*
@@ -45,7 +45,7 @@
* inode->i_lock
*
* inode_hash_lock
- * inode->i_sb->s_inode_list_lock
+ * inode->i_sb->s_inodes->lock
* inode->i_lock
*
* iunique_lock
@@ -424,19 +424,14 @@ static void inode_lru_list_del(struct inode *inode)
*/
void inode_sb_list_add(struct inode *inode)
{
- spin_lock(&inode->i_sb->s_inode_list_lock);
- list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
- spin_unlock(&inode->i_sb->s_inode_list_lock);
+ pcpu_list_add(&inode->i_sb_list, inode->i_sb->s_inodes);
}
EXPORT_SYMBOL_GPL(inode_sb_list_add);
static inline void inode_sb_list_del(struct inode *inode)
{
- if (!list_empty(&inode->i_sb_list)) {
- spin_lock(&inode->i_sb->s_inode_list_lock);
- list_del_init(&inode->i_sb_list);
- spin_unlock(&inode->i_sb->s_inode_list_lock);
- }
+ if (!list_empty(&inode->i_sb_list.list))
+ pcpu_list_del(&inode->i_sb_list);
}
static unsigned long hash(struct super_block *sb, unsigned long hashval)
@@ -590,12 +585,14 @@ static void dispose_list(struct list_head *head)
*/
void evict_inodes(struct super_block *sb)
{
- struct inode *inode, *next;
+ struct inode *inode;
+ struct pcpu_list_state state;
LIST_HEAD(dispose);
again:
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
+ init_pcpu_list_state(&state);
+ while (pcpu_list_iterate_safe(sb->s_inodes, &state)) {
+ inode = list_entry(state.curr, struct inode, i_sb_list);
if (atomic_read(&inode->i_count))
continue;
@@ -616,13 +613,12 @@ again:
* bit so we don't livelock.
*/
if (need_resched()) {
- spin_unlock(&sb->s_inode_list_lock);
+ spin_unlock(state.lock);
cond_resched();
dispose_list(&dispose);
goto again;
}
}
- spin_unlock(&sb->s_inode_list_lock);
dispose_list(&dispose);
}
@@ -640,11 +636,12 @@ again:
int invalidate_inodes(struct super_block *sb, bool kill_dirty)
{
int busy = 0;
- struct inode *inode, *next;
+ struct inode *inode;
LIST_HEAD(dispose);
+ DEFINE_PCPU_LIST_STATE(state);
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
+ while (pcpu_list_iterate_safe(sb->s_inodes, &state)) {
+ inode = list_entry(state.curr, struct inode, i_sb_list);
spin_lock(&inode->i_lock);
if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
spin_unlock(&inode->i_lock);
@@ -666,7 +663,6 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
spin_unlock(&inode->i_lock);
list_add(&inode->i_lru, &dispose);
}
- spin_unlock(&sb->s_inode_list_lock);
dispose_list(&dispose);
@@ -881,7 +877,7 @@ struct inode *new_inode_pseudo(struct super_block *sb)
spin_lock(&inode->i_lock);
inode->i_state = 0;
spin_unlock(&inode->i_lock);
- INIT_LIST_HEAD(&inode->i_sb_list);
+ init_pcpu_list_node(&inode->i_sb_list);
}
return inode;
}
@@ -902,8 +898,6 @@ struct inode *new_inode(struct super_block *sb)
{
struct inode *inode;
- spin_lock_prefetch(&sb->s_inode_list_lock);
-
inode = new_inode_pseudo(sb);
if (inode)
inode_sb_list_add(inode);
diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index a364524..12515a4 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -151,14 +151,15 @@ int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
void fsnotify_unmount_inodes(struct super_block *sb)
{
struct inode *inode, *iput_inode = NULL;
+ DEFINE_PCPU_LIST_STATE(state);
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ while (pcpu_list_iterate(sb->s_inodes, &state)) {
/*
* We cannot __iget() an inode in state I_FREEING,
* I_WILL_FREE, or I_NEW which is fine because by that point
* the inode cannot have any associated watches.
*/
+ inode = list_entry(state.curr, struct inode, i_sb_list);
spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
spin_unlock(&inode->i_lock);
@@ -178,7 +179,7 @@ void fsnotify_unmount_inodes(struct super_block *sb)
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ spin_unlock(state.lock);
if (iput_inode)
iput(iput_inode);
@@ -190,9 +191,8 @@ void fsnotify_unmount_inodes(struct super_block *sb)
iput_inode = inode;
- spin_lock(&sb->s_inode_list_lock);
+ spin_lock(state.lock);
}
- spin_unlock(&sb->s_inode_list_lock);
if (iput_inode)
iput(iput_inode);
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 3c3b81b..2564271 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -924,12 +924,13 @@ static int dqinit_needed(struct inode *inode, int type)
static void add_dquot_ref(struct super_block *sb, int type)
{
struct inode *inode, *old_inode = NULL;
+ DEFINE_PCPU_LIST_STATE(state);
#ifdef CONFIG_QUOTA_DEBUG
int reserved = 0;
#endif
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ while (pcpu_list_iterate(sb->s_inodes, &state)) {
+ inode = list_entry(state.curr, struct inode, i_sb_list);
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
!atomic_read(&inode->i_writecount) ||
@@ -939,7 +940,7 @@ static void add_dquot_ref(struct super_block *sb, int type)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ spin_unlock(state.lock);
#ifdef CONFIG_QUOTA_DEBUG
if (unlikely(inode_get_rsv_space(inode) > 0))
@@ -957,9 +958,8 @@ static void add_dquot_ref(struct super_block *sb, int type)
* later.
*/
old_inode = inode;
- spin_lock(&sb->s_inode_list_lock);
+ spin_lock(state.lock);
}
- spin_unlock(&sb->s_inode_list_lock);
iput(old_inode);
#ifdef CONFIG_QUOTA_DEBUG
@@ -1027,15 +1027,16 @@ static void remove_dquot_ref(struct super_block *sb, int type,
{
struct inode *inode;
int reserved = 0;
+ DEFINE_PCPU_LIST_STATE(state);
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ while (pcpu_list_iterate(sb->s_inodes, &state)) {
/*
* We have to scan also I_NEW inodes because they can already
* have quota pointer initialized. Luckily, we need to touch
* only quota pointers and these have separate locking
* (dq_data_lock).
*/
+ inode = list_entry(state.curr, struct inode, i_sb_list);
spin_lock(&dq_data_lock);
if (!IS_NOQUOTA(inode)) {
if (unlikely(inode_get_rsv_space(inode) > 0))
@@ -1044,7 +1045,6 @@ static void remove_dquot_ref(struct super_block *sb, int type,
}
spin_unlock(&dq_data_lock);
}
- spin_unlock(&sb->s_inode_list_lock);
#ifdef CONFIG_QUOTA_DEBUG
if (reserved) {
printk(KERN_WARNING "VFS (%s): Writes happened after quota"
diff --git a/fs/super.c b/fs/super.c
index 1182af8..7d44fad 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -163,6 +163,7 @@ static void destroy_super(struct super_block *s)
{
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
+ free_pcpu_list_head(&s->s_inodes);
security_sb_free(s);
WARN_ON(!list_empty(&s->s_mounts));
kfree(s->s_subtype);
@@ -204,9 +205,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_anon);
mutex_init(&s->s_sync_lock);
- INIT_LIST_HEAD(&s->s_inodes);
- spin_lock_init(&s->s_inode_list_lock);
+ if (init_pcpu_list_head(&s->s_inodes))
+ goto fail;
if (list_lru_init_memcg(&s->s_dentry_lru))
goto fail;
if (list_lru_init_memcg(&s->s_inode_lru))
@@ -426,7 +427,7 @@ void generic_shutdown_super(struct super_block *sb)
if (sop->put_super)
sop->put_super(sb);
- if (!list_empty(&sb->s_inodes)) {
+ if (!pcpu_list_empty(sb->s_inodes)) {
printk("VFS: Busy inodes after unmount of %s. "
"Self-destruct in 5 seconds. Have a nice day...\n",
sb->s_id);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ae68100..b533bda 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -28,6 +28,7 @@
#include <linux/uidgid.h>
#include <linux/lockdep.h>
#include <linux/percpu-rwsem.h>
+#include <linux/percpu-list.h>
#include <linux/blk_types.h>
#include <linux/workqueue.h>
#include <linux/percpu-rwsem.h>
@@ -648,7 +649,7 @@ struct inode {
u16 i_wb_frn_history;
#endif
struct list_head i_lru; /* inode LRU list */
- struct list_head i_sb_list;
+ struct pcpu_list_node i_sb_list;
union {
struct hlist_head i_dentry;
struct rcu_head i_rcu;
@@ -1397,9 +1398,8 @@ struct super_block {
*/
int s_stack_depth;
- /* s_inode_list_lock protects s_inodes */
- spinlock_t s_inode_list_lock ____cacheline_aligned_in_smp;
- struct list_head s_inodes; /* all inodes */
+ /* The percpu locks protect s_inodes */
+ struct pcpu_list_head __percpu *s_inodes; /* all inodes */
};
extern struct timespec current_fs_time(struct super_block *sb);
--
1.7.1