Commit fa3536cc authored by Eric Dumazet's avatar Eric Dumazet Committed by Linus Torvalds
Browse files

[PATCH] Use __read_mostly on some hot fs variables 



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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 878a9f30

fs/bio.c

+2 −2
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ 


#define BIO_POOL_SIZE 256



static kmem_cache_t *bio_slab;

static kmem_cache_t *bio_slab __read_mostly;



#define BIOVEC_NR_POOLS 6
@@ -39,7 +39,7 @@ static kmem_cache_t *bio_slab; 
 * basically we just need to survive

 */

#define BIO_SPLIT_ENTRIES 8	

mempool_t *bio_split_pool;

mempool_t *bio_split_pool __read_mostly;



struct biovec_slab {

	int nr_vecs;

fs/block_dev.c

+2 −2
Original line number Diff line number Diff line
@@ -234,7 +234,7 @@ static int block_fsync(struct file *filp, struct dentry *dentry, int datasync) 
 */



static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);

static kmem_cache_t * bdev_cachep;

static kmem_cache_t * bdev_cachep __read_mostly;



static struct inode *bdev_alloc_inode(struct super_block *sb)

{
@@ -308,7 +308,7 @@ static struct file_system_type bd_type = { 
	.kill_sb	= kill_anon_super,

};



static struct vfsmount *bd_mnt;

static struct vfsmount *bd_mnt __read_mostly;

struct super_block *blockdev_superblock;



void __init bdev_cache_init(void)

fs/dcache.c

+7 −7
Original line number Diff line number Diff line
@@ -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);

fs/dcookies.c

+3 −3
Original line number Diff line number Diff line
@@ -38,9 +38,9 @@ struct dcookie_struct { 


static LIST_HEAD(dcookie_users);

static DEFINE_MUTEX(dcookie_mutex);

static kmem_cache_t * dcookie_cache;

static struct list_head * dcookie_hashtable;

static size_t hash_size;

static kmem_cache_t *dcookie_cache __read_mostly;

static struct list_head *dcookie_hashtable __read_mostly;

static size_t hash_size __read_mostly;



static inline int is_live(void)

{

fs/dnotify.c

+2 −2
Original line number Diff line number Diff line
@@ -21,9 +21,9 @@ 
#include <linux/spinlock.h>

#include <linux/slab.h>



int dir_notify_enable = 1;

int dir_notify_enable __read_mostly = 1;



static kmem_cache_t *dn_cache;

static kmem_cache_t *dn_cache __read_mostly;



static void redo_inode_mask(struct inode *inode)

{