quota: Make quota stat accounting lockless.
Quota stats is mostly writable data structure. Let's alloc percpu
bucket for each value.
NOTE: dqstats_read() function is racy against dqstats_{inc,dec}
and may return inconsistent value. But this is ok since absolute
accuracy is not required.
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index ae76605..01347e8 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -82,7 +82,7 @@
/*
* There are three quota SMP locks. dq_list_lock protects all lists with quotas
- * and quota formats, dqstats structure containing statistics about the lists
+ * and quota formats.
* dq_data_lock protects data from dq_dqb and also mem_dqinfo structures and
* also guards consistency of dquot->dq_dqb with inode->i_blocks, i_bytes.
* i_blocks and i_bytes updates itself are guarded by i_lock acquired directly
@@ -228,6 +228,10 @@
struct dqstats dqstats;
EXPORT_SYMBOL(dqstats);
+#ifdef CONFIG_SMP
+struct dqstats *dqstats_pcpu;
+EXPORT_SYMBOL(dqstats_pcpu);
+#endif
static qsize_t inode_get_rsv_space(struct inode *inode);
static void __dquot_initialize(struct inode *inode, int type);
@@ -275,7 +279,7 @@
static inline void put_dquot_last(struct dquot *dquot)
{
list_add_tail(&dquot->dq_free, &free_dquots);
- dqstats.free_dquots++;
+ dqstats_inc(DQST_FREE_DQUOTS);
}
static inline void remove_free_dquot(struct dquot *dquot)
@@ -283,7 +287,7 @@
if (list_empty(&dquot->dq_free))
return;
list_del_init(&dquot->dq_free);
- dqstats.free_dquots--;
+ dqstats_dec(DQST_FREE_DQUOTS);
}
static inline void put_inuse(struct dquot *dquot)
@@ -291,12 +295,12 @@
/* We add to the back of inuse list so we don't have to restart
* when traversing this list and we block */
list_add_tail(&dquot->dq_inuse, &inuse_list);
- dqstats.allocated_dquots++;
+ dqstats_inc(DQST_ALLOC_DQUOTS);
}
static inline void remove_inuse(struct dquot *dquot)
{
- dqstats.allocated_dquots--;
+ dqstats_dec(DQST_ALLOC_DQUOTS);
list_del(&dquot->dq_inuse);
}
/*
@@ -561,8 +565,8 @@
continue;
/* Now we have active dquot so we can just increase use count */
atomic_inc(&dquot->dq_count);
- dqstats.lookups++;
spin_unlock(&dq_list_lock);
+ dqstats_inc(DQST_LOOKUPS);
dqput(old_dquot);
old_dquot = dquot;
ret = fn(dquot, priv);
@@ -607,8 +611,8 @@
* holding reference so we can safely just increase
* use count */
atomic_inc(&dquot->dq_count);
- dqstats.lookups++;
spin_unlock(&dq_list_lock);
+ dqstats_inc(DQST_LOOKUPS);
sb->dq_op->write_dquot(dquot);
dqput(dquot);
spin_lock(&dq_list_lock);
@@ -620,9 +624,7 @@
if ((cnt == type || type == -1) && sb_has_quota_active(sb, cnt)
&& info_dirty(&dqopt->info[cnt]))
sb->dq_op->write_info(sb, cnt);
- spin_lock(&dq_list_lock);
- dqstats.syncs++;
- spin_unlock(&dq_list_lock);
+ dqstats_inc(DQST_SYNCS);
mutex_unlock(&dqopt->dqonoff_mutex);
if (!wait || (sb_dqopt(sb)->flags & DQUOT_QUOTA_SYS_FILE))
@@ -674,6 +676,22 @@
}
}
+static int dqstats_read(unsigned int type)
+{
+ int count = 0;
+#ifdef CONFIG_SMP
+ int cpu;
+ for_each_possible_cpu(cpu)
+ count += per_cpu_ptr(dqstats_pcpu, cpu)->stat[type];
+ /* Statistics reading is racy, but absolute accuracy isn't required */
+ if (count < 0)
+ count = 0;
+#else
+ count = dqstats.stat[type];
+#endif
+ return count;
+}
+
/*
* This is called from kswapd when we think we need some
* more memory
@@ -686,7 +704,7 @@
prune_dqcache(nr);
spin_unlock(&dq_list_lock);
}
- return (dqstats.free_dquots / 100) * sysctl_vfs_cache_pressure;
+ return (dqstats_read(DQST_FREE_DQUOTS)/100) * sysctl_vfs_cache_pressure;
}
static struct shrinker dqcache_shrinker = {
@@ -714,10 +732,7 @@
BUG();
}
#endif
-
- spin_lock(&dq_list_lock);
- dqstats.drops++;
- spin_unlock(&dq_list_lock);
+ dqstats_inc(DQST_DROPS);
we_slept:
spin_lock(&dq_list_lock);
if (atomic_read(&dquot->dq_count) > 1) {
@@ -834,15 +849,15 @@
put_inuse(dquot);
/* hash it first so it can be found */
insert_dquot_hash(dquot);
- dqstats.lookups++;
spin_unlock(&dq_list_lock);
+ dqstats_inc(DQST_LOOKUPS);
} else {
if (!atomic_read(&dquot->dq_count))
remove_free_dquot(dquot);
atomic_inc(&dquot->dq_count);
- dqstats.cache_hits++;
- dqstats.lookups++;
spin_unlock(&dq_list_lock);
+ dqstats_inc(DQST_CACHE_HITS);
+ dqstats_inc(DQST_LOOKUPS);
}
/* Wait for dq_lock - after this we know that either dquot_release() is
* already finished or it will be canceled due to dq_count > 1 test */
@@ -2476,62 +2491,74 @@
.set_dqblk = vfs_set_dqblk
};
+
+static int do_proc_dqstats(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+#ifdef CONFIG_SMP
+ /* Update global table */
+ unsigned int type = (int *)table->data - dqstats.stat;
+ dqstats.stat[type] = dqstats_read(type);
+#endif
+ return proc_dointvec(table, write, buffer, lenp, ppos);
+}
+
static ctl_table fs_dqstats_table[] = {
{
.procname = "lookups",
- .data = &dqstats.lookups,
+ .data = &dqstats.stat[DQST_LOOKUPS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "drops",
- .data = &dqstats.drops,
+ .data = &dqstats.stat[DQST_DROPS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "reads",
- .data = &dqstats.reads,
+ .data = &dqstats.stat[DQST_READS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "writes",
- .data = &dqstats.writes,
+ .data = &dqstats.stat[DQST_WRITES],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "cache_hits",
- .data = &dqstats.cache_hits,
+ .data = &dqstats.stat[DQST_CACHE_HITS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "allocated_dquots",
- .data = &dqstats.allocated_dquots,
+ .data = &dqstats.stat[DQST_ALLOC_DQUOTS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "free_dquots",
- .data = &dqstats.free_dquots,
+ .data = &dqstats.stat[DQST_FREE_DQUOTS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
{
.procname = "syncs",
- .data = &dqstats.syncs,
+ .data = &dqstats.stat[DQST_SYNCS],
.maxlen = sizeof(int),
.mode = 0444,
- .proc_handler = proc_dointvec,
+ .proc_handler = do_proc_dqstats,
},
#ifdef CONFIG_PRINT_QUOTA_WARNING
{
@@ -2583,6 +2610,13 @@
if (!dquot_hash)
panic("Cannot create dquot hash table");
+#ifdef CONFIG_SMP
+ dqstats_pcpu = alloc_percpu(struct dqstats);
+ if (!dqstats_pcpu)
+ panic("Cannot create dquot stats table");
+#endif
+ memset(&dqstats, 0, sizeof(struct dqstats));
+
/* Find power-of-two hlist_heads which can fit into allocation */
nr_hash = (1UL << order) * PAGE_SIZE / sizeof(struct hlist_head);
dq_hash_bits = 0;