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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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8
fs/inode.c
View file

@ -56,8 +56,8 @@
#define I_HASHBITS i_hash_shift
#define I_HASHMASK i_hash_mask
static unsigned int i_hash_mask;
static unsigned int i_hash_shift;
static unsigned int i_hash_mask __read_mostly;
static unsigned int i_hash_shift __read_mostly;
/*
* Each inode can be on two separate lists. One is
@ -73,7 +73,7 @@ static unsigned int i_hash_shift;
LIST_HEAD(inode_in_use);
LIST_HEAD(inode_unused);
static struct hlist_head *inode_hashtable;
static struct hlist_head *inode_hashtable __read_mostly;
/*
* A simple spinlock to protect the list manipulations.
@ -98,7 +98,7 @@ static DEFINE_MUTEX(iprune_mutex);
*/
struct inodes_stat_t inodes_stat;
static kmem_cache_t * inode_cachep;
static kmem_cache_t * inode_cachep __read_mostly;
static struct inode *alloc_inode(struct super_block *sb)
{