[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: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/bio.c b/fs/bio.c
index 73e664c..49db928 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -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 @@
* 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;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 573fc8e..9a451a9 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -234,7 +234,7 @@
*/
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 @@
.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)
diff --git a/fs/dcache.c b/fs/dcache.c
index 93958464..aaca5e7 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -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 @@
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 @@
#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 @@
}
/* 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);
diff --git a/fs/dcookies.c b/fs/dcookies.c
index ef758cf..8749339 100644
--- a/fs/dcookies.c
+++ b/fs/dcookies.c
@@ -38,9 +38,9 @@
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)
{
diff --git a/fs/dnotify.c b/fs/dnotify.c
index f3b540d..f932591 100644
--- a/fs/dnotify.c
+++ b/fs/dnotify.c
@@ -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)
{
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index a0f682c..e067a06 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -281,13 +281,13 @@
static struct poll_safewake psw;
/* Slab cache used to allocate "struct epitem" */
-static kmem_cache_t *epi_cache;
+static kmem_cache_t *epi_cache __read_mostly;
/* Slab cache used to allocate "struct eppoll_entry" */
-static kmem_cache_t *pwq_cache;
+static kmem_cache_t *pwq_cache __read_mostly;
/* Virtual fs used to allocate inodes for eventpoll files */
-static struct vfsmount *eventpoll_mnt;
+static struct vfsmount *eventpoll_mnt __read_mostly;
/* File callbacks that implement the eventpoll file behaviour */
static struct file_operations eventpoll_fops = {
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 03c7895..2a24791 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -412,7 +412,7 @@
/* Table to convert sigio signal codes into poll band bitmaps */
-static long band_table[NSIGPOLL] = {
+static const long band_table[NSIGPOLL] = {
POLLIN | POLLRDNORM, /* POLL_IN */
POLLOUT | POLLWRNORM | POLLWRBAND, /* POLL_OUT */
POLLIN | POLLRDNORM | POLLMSG, /* POLL_MSG */
@@ -531,7 +531,7 @@
}
static DEFINE_RWLOCK(fasync_lock);
-static kmem_cache_t *fasync_cache;
+static kmem_cache_t *fasync_cache __read_mostly;
/*
* fasync_helper() is used by some character device drivers (mainly mice)
diff --git a/fs/inode.c b/fs/inode.c
index 85da110..1fddf28 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -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 @@
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 @@
*/
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)
{
diff --git a/fs/inotify.c b/fs/inotify.c
index a61e93e..f48a3da 100644
--- a/fs/inotify.c
+++ b/fs/inotify.c
@@ -39,15 +39,15 @@
static atomic_t inotify_cookie;
-static kmem_cache_t *watch_cachep;
-static kmem_cache_t *event_cachep;
+static kmem_cache_t *watch_cachep __read_mostly;
+static kmem_cache_t *event_cachep __read_mostly;
-static struct vfsmount *inotify_mnt;
+static struct vfsmount *inotify_mnt __read_mostly;
/* these are configurable via /proc/sys/fs/inotify/ */
-int inotify_max_user_instances;
-int inotify_max_user_watches;
-int inotify_max_queued_events;
+int inotify_max_user_instances __read_mostly;
+int inotify_max_user_watches __read_mostly;
+int inotify_max_queued_events __read_mostly;
/*
* Lock ordering:
diff --git a/fs/locks.c b/fs/locks.c
index 56f996e..709450a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -142,7 +142,7 @@
static LIST_HEAD(file_lock_list);
static LIST_HEAD(blocked_list);
-static kmem_cache_t *filelock_cache;
+static kmem_cache_t *filelock_cache __read_mostly;
/* Allocate an empty lock structure. */
static struct file_lock *locks_alloc_lock(void)
diff --git a/fs/namespace.c b/fs/namespace.c
index 71e75bc..e069a4c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -43,9 +43,9 @@
static int event;
-static struct list_head *mount_hashtable;
+static struct list_head *mount_hashtable __read_mostly;
static int hash_mask __read_mostly, hash_bits __read_mostly;
-static kmem_cache_t *mnt_cache;
+static kmem_cache_t *mnt_cache __read_mostly;
static struct rw_semaphore namespace_sem;
/* /sys/fs */
diff --git a/fs/pipe.c b/fs/pipe.c
index d976866..4384c92 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -675,7 +675,7 @@
return NULL;
}
-static struct vfsmount *pipe_mnt;
+static struct vfsmount *pipe_mnt __read_mostly;
static int pipefs_delete_dentry(struct dentry *dentry)
{
return 1;