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inode: Make unused inode LRU per superblock 

The inode unused list is currently a global LRU. This does not match
the other global filesystem cache - the dentry cache - which uses
per-superblock LRU lists. Hence we have related filesystem object
types using different LRU reclaimation schemes.

To enable a per-superblock filesystem cache shrinker, both of these
caches need to have per-sb unused object LRU lists. Hence this patch
converts the global inode LRU to per-sb LRUs.

The patch only does rudimentary per-sb propotioning in the shrinker
infrastructure, as this gets removed when the per-sb shrinker
callouts are introduced later on.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Dave Chinner 2011-07-08 14:14:39 +10:00 committed by Al Viro
parent fcb94f72d3
commit 98b745c647
3 changed files with 85 additions and 11 deletions
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91
fs/inode.c
View File

@ -34,7 +34,7 @@
* inode->i_lock protects:
* inode->i_state, inode->i_hash, __iget()
* inode_lru_lock protects:
* inode_lru, inode->i_lru
* inode->i_sb->s_inode_lru, inode->i_lru
* inode_sb_list_lock protects:
* sb->s_inodes, inode->i_sb_list
* inode_wb_list_lock protects:
@ -64,7 +64,6 @@ static unsigned int i_hash_shift __read_mostly;
static struct hlist_head *inode_hashtable __read_mostly;
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
static LIST_HEAD(inode_lru);
static DEFINE_SPINLOCK(inode_lru_lock);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
@ -345,7 +344,8 @@ static void inode_lru_list_add(struct inode *inode)
{
spin_lock(&inode_lru_lock);
if (list_empty(&inode->i_lru)) {
list_add(&inode->i_lru, &inode_lru);
list_add(&inode->i_lru, &inode->i_sb->s_inode_lru);
inode->i_sb->s_nr_inodes_unused++;
this_cpu_inc(nr_unused);
}
spin_unlock(&inode_lru_lock);
@ -356,6 +356,7 @@ static void inode_lru_list_del(struct inode *inode)
spin_lock(&inode_lru_lock);
if (!list_empty(&inode->i_lru)) {
list_del_init(&inode->i_lru);
inode->i_sb->s_nr_inodes_unused--;
this_cpu_dec(nr_unused);
}
spin_unlock(&inode_lru_lock);
@ -628,21 +629,20 @@ static int can_unuse(struct inode *inode)
* LRU does not have strict ordering. Hence we don't want to reclaim inodes
* with this flag set because they are the inodes that are out of order.
*/
static void prune_icache(int nr_to_scan)
static void shrink_icache_sb(struct super_block *sb, int *nr_to_scan)
{
LIST_HEAD(freeable);
int nr_scanned;
unsigned long reap = 0;
down_read(&iprune_sem);
spin_lock(&inode_lru_lock);
for (nr_scanned = 0; nr_scanned < nr_to_scan; nr_scanned++) {
for (nr_scanned = *nr_to_scan; nr_scanned >= 0; nr_scanned--) {
struct inode *inode;
if (list_empty(&inode_lru))
if (list_empty(&sb->s_inode_lru))
break;
inode = list_entry(inode_lru.prev, struct inode, i_lru);
inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
/*
* we are inverting the inode_lru_lock/inode->i_lock here,
@ -650,7 +650,7 @@ static void prune_icache(int nr_to_scan)
* inode to the back of the list so we don't spin on it.
*/
if (!spin_trylock(&inode->i_lock)) {
list_move(&inode->i_lru, &inode_lru);
list_move(&inode->i_lru, &sb->s_inode_lru);
continue;
}
@ -662,6 +662,7 @@ static void prune_icache(int nr_to_scan)
(inode->i_state & ~I_REFERENCED)) {
list_del_init(&inode->i_lru);
spin_unlock(&inode->i_lock);
sb->s_nr_inodes_unused--;
this_cpu_dec(nr_unused);
continue;
}
@ -669,7 +670,7 @@ static void prune_icache(int nr_to_scan)
/* recently referenced inodes get one more pass */
if (inode->i_state & I_REFERENCED) {
inode->i_state &= ~I_REFERENCED;
list_move(&inode->i_lru, &inode_lru);
list_move(&inode->i_lru, &sb->s_inode_lru);
spin_unlock(&inode->i_lock);
continue;
}
@ -683,7 +684,7 @@ static void prune_icache(int nr_to_scan)
iput(inode);
spin_lock(&inode_lru_lock);
if (inode != list_entry(inode_lru.next,
if (inode != list_entry(sb->s_inode_lru.next,
struct inode, i_lru))
continue; /* wrong inode or list_empty */
/* avoid lock inversions with trylock */
@ -699,6 +700,7 @@ static void prune_icache(int nr_to_scan)
spin_unlock(&inode->i_lock);
list_move(&inode->i_lru, &freeable);
sb->s_nr_inodes_unused--;
this_cpu_dec(nr_unused);
}
if (current_is_kswapd())
@ -706,8 +708,75 @@ static void prune_icache(int nr_to_scan)
else
__count_vm_events(PGINODESTEAL, reap);
spin_unlock(&inode_lru_lock);
*nr_to_scan = nr_scanned;
dispose_list(&freeable);
}
static void prune_icache(int count)
{
struct super_block *sb, *p = NULL;
int w_count;
int unused = inodes_stat.nr_unused;
int prune_ratio;
int pruned;
if (unused == 0 || count == 0)
return;
down_read(&iprune_sem);
if (count >= unused)
prune_ratio = 1;
else
prune_ratio = unused / count;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (list_empty(&sb->s_instances))
continue;
if (sb->s_nr_inodes_unused == 0)
continue;
sb->s_count++;
/* Now, we reclaim unused dentrins with fairness.
* We reclaim them same percentage from each superblock.
* We calculate number of dentries to scan on this sb
* as follows, but the implementation is arranged to avoid
* overflows:
* number of dentries to scan on this sb =
* count * (number of dentries on this sb /
* number of dentries in the machine)
*/
spin_unlock(&sb_lock);
if (prune_ratio != 1)
w_count = (sb->s_nr_inodes_unused / prune_ratio) + 1;
else
w_count = sb->s_nr_inodes_unused;
pruned = w_count;
/*
* We need to be sure this filesystem isn't being unmounted,
* otherwise we could race with generic_shutdown_super(), and
* end up holding a reference to an inode while the filesystem
* is unmounted. So we try to get s_umount, and make sure
* s_root isn't NULL.
*/
if (down_read_trylock(&sb->s_umount)) {
if ((sb->s_root != NULL) &&
(!list_empty(&sb->s_dentry_lru))) {
shrink_icache_sb(sb, &w_count);
pruned -= w_count;
}
up_read(&sb->s_umount);
}
spin_lock(&sb_lock);
if (p)
__put_super(p);
count -= pruned;
p = sb;
/* more work left to do? */
if (count <= 0)
break;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
up_read(&iprune_sem);
}

1
fs/super.c
View File

@ -77,6 +77,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
INIT_HLIST_BL_HEAD(&s->s_anon);
INIT_LIST_HEAD(&s->s_inodes);
INIT_LIST_HEAD(&s->s_dentry_lru);
INIT_LIST_HEAD(&s->s_inode_lru);
init_rwsem(&s->s_umount);
mutex_init(&s->s_lock);
lockdep_set_class(&s->s_umount, &type->s_umount_key);

4
include/linux/fs.h
View File

@ -1397,6 +1397,10 @@ struct super_block {
struct list_head s_dentry_lru; /* unused dentry lru */
int s_nr_dentry_unused; /* # of dentry on lru */
/* inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
struct list_head s_inode_lru; /* unused inode lru */
int s_nr_inodes_unused; /* # of inodes on lru */
struct block_device *s_bdev;
struct backing_dev_info *s_bdi;
struct mtd_info *s_mtd;