From dde9588853b1bde542eab247f8838c472806688f Mon Sep 17 00:00:00 2001 From: Dmitry Monakhov Date: Mon, 26 Apr 2010 20:03:33 +0400 Subject: 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 Signed-off-by: Jan Kara --- fs/quota/dquot.c | 102 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 68 insertions(+), 34 deletions(-) (limited to 'fs/quota/dquot.c') diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c index ae766056350d..01347e81d0ca 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 @@ static struct hlist_head *dquot_hash; 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 struct dquot *find_dquot(unsigned int hashent, struct super_block *sb, 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 @@ static inline void remove_free_dquot(struct dquot *dquot) 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 @@ static inline void put_inuse(struct dquot *dquot) /* 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 @@ int dquot_scan_active(struct super_block *sb, 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 @@ int vfs_quota_sync(struct super_block *sb, int type, int wait) * 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 @@ int vfs_quota_sync(struct super_block *sb, int type, int wait) 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 void prune_dqcache(int count) } } +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 @@ static int shrink_dqcache_memory(int nr, gfp_t gfp_mask) 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 @@ void dqput(struct dquot *dquot) 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 @@ we_slept: 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 @@ const struct quotactl_ops vfs_quotactl_ops = { .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 @@ static int __init dquot_init(void) 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; -- cgit v1.2.3-59-g8ed1b