[patch 21/35] fs: icache per-cpu nr_inodes, non-atomic nr_unused counters
From: npiggin
Date: Mon Oct 18 2010 - 23:57:44 EST
From: Eric Dumazet <eric.dumazet@xxxxxxxxx>
[Eric Dumazet]
Make nr_inodes a per-cpu counter to avoid cache line ping pongs between cpus.
[Nick Piggin]
Make nr_unused non-atomic and protected by wb_inode_list_lock.
Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: Nick Piggin <npiggin@xxxxxxxxx>
---
fs/fs-writeback.c | 18 +++++++++++-----
fs/inode.c | 58 ++++++++++++++++++++++++++++++++++++++---------------
include/linux/fs.h | 15 +++++--------
kernel/sysctl.c | 4 +--
4 files changed, 63 insertions(+), 32 deletions(-)
Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c 2010-10-19 14:38:03.000000000 +1100
+++ linux-2.6/fs/inode.c 2010-10-19 14:38:27.000000000 +1100
@@ -139,12 +139,42 @@
* Statistics gathering..
*/
struct inodes_stat_t inodes_stat = {
- .nr_inodes = ATOMIC_INIT(0),
- .nr_unused = ATOMIC_INIT(0),
+ .nr_inodes = 0,
+ .nr_unused = 0,
};
+static DEFINE_PER_CPU(unsigned int, nr_inodes);
+
static struct kmem_cache *inode_cachep __read_mostly;
+int get_nr_inodes(void)
+{
+ int i;
+ int sum = 0;
+ for_each_possible_cpu(i)
+ sum += per_cpu(nr_inodes, i);
+ return sum < 0 ? 0 : sum;
+}
+
+int get_nr_inodes_unused(void)
+{
+ return inodes_stat.nr_unused;
+}
+
+/*
+ * Handle nr_dentry sysctl
+ */
+int proc_nr_inodes(ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+ inodes_stat.nr_inodes = get_nr_inodes();
+ return proc_dointvec(table, write, buffer, lenp, ppos);
+#else
+ return -ENOSYS;
+#endif
+}
+
static void wake_up_inode(struct inode *inode)
{
/*
@@ -232,7 +262,7 @@
inode->i_fsnotify_mask = 0;
#endif
- atomic_inc(&inodes_stat.nr_inodes);
+ this_cpu_inc(nr_inodes);
return 0;
out:
@@ -280,7 +310,7 @@
if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
posix_acl_release(inode->i_default_acl);
#endif
- atomic_dec(&inodes_stat.nr_inodes);
+ this_cpu_dec(nr_inodes);
}
EXPORT_SYMBOL(__destroy_inode);
@@ -400,7 +430,7 @@
static int invalidate_list(struct list_head *head, struct list_head *dispose)
{
struct list_head *next;
- int busy = 0, count = 0;
+ int busy = 0;
next = head->next;
for (;;) {
@@ -420,19 +450,17 @@
if (!inode->i_count) {
spin_lock(&wb_inode_list_lock);
list_del(&inode->i_list);
+ inodes_stat.nr_unused--;
spin_unlock(&wb_inode_list_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
spin_unlock(&inode->i_lock);
list_add(&inode->i_list, dispose);
- count++;
continue;
}
spin_unlock(&inode->i_lock);
busy = 1;
}
- /* only unused inodes may be cached with i_count zero */
- atomic_sub(count, &inodes_stat.nr_unused);
return busy;
}
@@ -494,7 +522,6 @@
static void prune_icache(unsigned long nr_to_scan)
{
LIST_HEAD(freeable);
- int nr_pruned = 0;
unsigned long reap = 0;
down_read(&iprune_sem);
@@ -515,7 +542,7 @@
if (inode->i_count || (inode->i_state & ~I_REFERENCED)) {
list_del_init(&inode->i_list);
spin_unlock(&inode->i_lock);
- atomic_dec(&inodes_stat.nr_unused);
+ inodes_stat.nr_unused--;
continue;
}
if (inode->i_state & I_REFERENCED) {
@@ -557,9 +584,8 @@
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
spin_unlock(&inode->i_lock);
- nr_pruned++;
+ inodes_stat.nr_unused--;
}
- atomic_sub(nr_pruned, &inodes_stat.nr_unused);
if (current_is_kswapd())
__count_vm_events(KSWAPD_INODESTEAL, reap);
else
@@ -587,7 +613,7 @@
unsigned long nr;
shrinker_add_scan(&nr_to_scan, scanned, global,
- atomic_read(&inodes_stat.nr_unused),
+ inodes_stat.nr_unused,
SHRINK_DEFAULT_SEEKS * 100 / sysctl_vfs_cache_pressure);
/*
* Nasty deadlock avoidance. We may hold various FS locks,
@@ -1372,8 +1398,8 @@
list_empty(&inode->i_list)) {
spin_lock(&wb_inode_list_lock);
list_add(&inode->i_list, &inode_unused);
+ inodes_stat.nr_unused++;
spin_unlock(&wb_inode_list_lock);
- atomic_inc(&inodes_stat.nr_unused);
}
spin_unlock(&inode->i_lock);
return;
@@ -1390,9 +1416,9 @@
if (!list_empty(&inode->i_list)) {
spin_lock(&wb_inode_list_lock);
list_del_init(&inode->i_list);
- spin_unlock(&wb_inode_list_lock);
if (!inode->i_state)
- atomic_dec(&inodes_stat.nr_unused);
+ inodes_stat.nr_unused--;
+ spin_unlock(&wb_inode_list_lock);
}
spin_lock(&sb_inode_list_lock);
list_del_rcu(&inode->i_sb_list);
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2010-10-19 14:38:03.000000000 +1100
+++ linux-2.6/include/linux/fs.h 2010-10-19 14:38:05.000000000 +1100
@@ -40,14 +40,8 @@
};
struct inodes_stat_t {
- /*
- * Using atomics here is a hack which should just happen to
- * work on all architectures today. Not a big deal though,
- * because it goes away and gets fixed properly later in the
- * inode scaling series.
- */
- atomic_t nr_inodes;
- atomic_t nr_unused;
+ int nr_inodes;
+ int nr_unused;
int dummy[5]; /* padding for sysctl ABI compatibility */
};
@@ -413,6 +407,8 @@
extern int get_max_files(void);
extern int sysctl_nr_open;
extern struct inodes_stat_t inodes_stat;
+extern int get_nr_inodes(void);
+extern int get_nr_inodes_unused(void);
extern int leases_enable, lease_break_time;
struct buffer_head;
@@ -2490,7 +2486,8 @@
struct ctl_table;
int proc_nr_files(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
-
+int proc_nr_inodes(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
int __init get_filesystem_list(char *buf);
#define ACC_MODE(x) ("\004\002\006\006"[(x)&O_ACCMODE])
Index: linux-2.6/fs/fs-writeback.c
===================================================================
--- linux-2.6.orig/fs/fs-writeback.c 2010-10-19 14:38:03.000000000 +1100
+++ linux-2.6/fs/fs-writeback.c 2010-10-19 14:38:05.000000000 +1100
@@ -738,6 +738,7 @@
{
unsigned long expired;
long nr_pages;
+ int nr_dirty_inodes;
/*
* When set to zero, disable periodic writeback
@@ -750,11 +751,15 @@
if (time_before(jiffies, expired))
return 0;
+ /* approximate dirty inodes */
+ nr_dirty_inodes = get_nr_inodes() - get_nr_inodes_unused();
+ if (nr_dirty_inodes < 0)
+ nr_dirty_inodes = 0;
+
wb->last_old_flush = jiffies;
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
- (atomic_read(&inodes_stat.nr_inodes) -
- atomic_read(&inodes_stat.nr_unused));
+ nr_dirty_inodes;
if (nr_pages) {
struct wb_writeback_work work = {
@@ -1120,6 +1125,7 @@
{
unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
+ int nr_dirty_inodes;
DECLARE_COMPLETION_ONSTACK(done);
struct wb_writeback_work work = {
.sb = sb,
@@ -1129,9 +1135,11 @@
WARN_ON(!rwsem_is_locked(&sb->s_umount));
- work.nr_pages = nr_dirty + nr_unstable +
- (atomic_read(&inodes_stat.nr_inodes) -
- atomic_read(&inodes_stat.nr_unused));
+ nr_dirty_inodes = get_nr_inodes() - get_nr_inodes_unused();
+ if (nr_dirty_inodes < 0)
+ nr_dirty_inodes = 0;
+
+ work.nr_pages = nr_dirty + nr_unstable + nr_dirty_inodes;
bdi_queue_work(sb->s_bdi, &work);
wait_for_completion(&done);
Index: linux-2.6/kernel/sysctl.c
===================================================================
--- linux-2.6.orig/kernel/sysctl.c 2010-10-19 14:19:24.000000000 +1100
+++ linux-2.6/kernel/sysctl.c 2010-10-19 14:38:05.000000000 +1100
@@ -1340,14 +1340,14 @@
.data = &inodes_stat,
.maxlen = 2*sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_nr_inodes,
},
{
.procname = "inode-state",
.data = &inodes_stat,
.maxlen = 7*sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_nr_inodes,
},
{
.procname = "file-nr",
--
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