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[PATCH] Use __read_mostly on some hot fs variables

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I discovered on oprofile hunting on a SMP platform that dentry lookups were
slowed down because d_hash_mask, d_hash_shift and dentry_hashtable were in
a cache line that contained inodes_stat.  So each time inodes_stats is
changed by a cpu, other cpus have to refill their cache line.

This patch moves some variables to the __read_mostly section, in order to
avoid false sharing.  RCU dentry lookups can go full speed.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Eric Dumazet
2006-03-26 01:37:24 -08:00
committed by Linus Torvalds
parent 878a9f30d7
commit fa3536cc14
12 changed files with 35 additions and 35 deletions
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14
fs/dcache.c
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@ -36,7 +36,7 @@
/* #define DCACHE_DEBUG 1 */
int sysctl_vfs_cache_pressure = 100;
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
@ -44,7 +44,7 @@ static seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
EXPORT_SYMBOL(dcache_lock);
static kmem_cache_t *dentry_cache;
static kmem_cache_t *dentry_cache __read_mostly;
#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
@ -59,9 +59,9 @@ static kmem_cache_t *dentry_cache;
#define D_HASHBITS d_hash_shift
#define D_HASHMASK d_hash_mask
static unsigned int d_hash_mask;
static unsigned int d_hash_shift;
static struct hlist_head *dentry_hashtable;
static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
static struct hlist_head *dentry_hashtable __read_mostly;
static LIST_HEAD(dentry_unused);
/* Statistics gathering. */
@ -1719,10 +1719,10 @@ static void __init dcache_init(unsigned long mempages)
}
/* SLAB cache for __getname() consumers */
kmem_cache_t *names_cachep;
kmem_cache_t *names_cachep __read_mostly;
/* SLAB cache for file structures */
kmem_cache_t *filp_cachep;
kmem_cache_t *filp_cachep __read_mostly;
EXPORT_SYMBOL(d_genocide);