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authorEric Dumazet <dada1@cosmosbay.com>2006-01-08 01:03:32 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-08 20:13:58 -0800
commit5160ee6fc891a9ca114be0e90fa6655647bb64b2 (patch)
tree35d3740a777935582af1b78238f20d2c2971ed55 /fs/autofs4
parent21b6bf143d05d77c350d9c6764ae090a877b66ea (diff)
[PATCH] shrink dentry struct
Some long time ago, dentry struct was carefully tuned so that on 32 bits UP, sizeof(struct dentry) was exactly 128, ie a power of 2, and a multiple of memory cache lines. Then RCU was added and dentry struct enlarged by two pointers, with nice results for SMP, but not so good on UP, because breaking the above tuning (128 + 8 = 136 bytes) This patch reverts this unwanted side effect, by using an union (d_u), where d_rcu and d_child are placed so that these two fields can share their memory needs. At the time d_free() is called (and d_rcu is really used), d_child is known to be empty and not touched by the dentry freeing. Lockless lookups only access d_name, d_parent, d_lock, d_op, d_flags (so the previous content of d_child is not needed if said dentry was unhashed but still accessed by a CPU because of RCU constraints) As dentry cache easily contains millions of entries, a size reduction is worth the extra complexity of the ugly C union. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Cc: Dipankar Sarma <dipankar@in.ibm.com> Cc: Maneesh Soni <maneesh@in.ibm.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Ian Kent <raven@themaw.net> Cc: Paul Jackson <pj@sgi.com> Cc: Al Viro <viro@ftp.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Neil Brown <neilb@cse.unsw.edu.au> Cc: James Morris <jmorris@namei.org> Cc: Stephen Smalley <sds@epoch.ncsc.mil> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/autofs4')
-rw-r--r--fs/autofs4/autofs_i.h2
-rw-r--r--fs/autofs4/expire.c12
-rw-r--r--fs/autofs4/inode.c4
-rw-r--r--fs/autofs4/root.c3
4 files changed, 11 insertions, 10 deletions
diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index fca83e28edc..385bed09b0d 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -209,7 +209,7 @@ static inline int simple_empty_nolock(struct dentry *dentry)
struct dentry *child;
int ret = 0;
- list_for_each_entry(child, &dentry->d_subdirs, d_child)
+ list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
if (simple_positive(child))
goto out;
ret = 1;
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index feb6ac427d0..dc39589df16 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -105,7 +105,7 @@ repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
- struct dentry *dentry = list_entry(next, struct dentry, d_child);
+ struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
/* Negative dentry - give up */
if (!simple_positive(dentry)) {
@@ -138,7 +138,7 @@ resume:
}
if (this_parent != top) {
- next = this_parent->d_child.next;
+ next = this_parent->d_u.d_child.next;
this_parent = this_parent->d_parent;
goto resume;
}
@@ -163,7 +163,7 @@ repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
- struct dentry *dentry = list_entry(next, struct dentry, d_child);
+ struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
/* Negative dentry - give up */
if (!simple_positive(dentry)) {
@@ -199,7 +199,7 @@ cont:
}
if (this_parent != parent) {
- next = this_parent->d_child.next;
+ next = this_parent->d_u.d_child.next;
this_parent = this_parent->d_parent;
goto resume;
}
@@ -238,7 +238,7 @@ static struct dentry *autofs4_expire(struct super_block *sb,
/* On exit from the loop expire is set to a dgot dentry
* to expire or it's NULL */
while ( next != &root->d_subdirs ) {
- struct dentry *dentry = list_entry(next, struct dentry, d_child);
+ struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
/* Negative dentry - give up */
if ( !simple_positive(dentry) ) {
@@ -302,7 +302,7 @@ next:
expired, (int)expired->d_name.len, expired->d_name.name);
spin_lock(&dcache_lock);
list_del(&expired->d_parent->d_subdirs);
- list_add(&expired->d_parent->d_subdirs, &expired->d_child);
+ list_add(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
spin_unlock(&dcache_lock);
return expired;
}
diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index 818b37be515..2d3082854a2 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -91,7 +91,7 @@ repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
- struct dentry *dentry = list_entry(next, struct dentry, d_child);
+ struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
/* Negative dentry - don`t care */
if (!simple_positive(dentry)) {
@@ -117,7 +117,7 @@ resume:
if (this_parent != sbi->root) {
struct dentry *dentry = this_parent;
- next = this_parent->d_child.next;
+ next = this_parent->d_u.d_child.next;
this_parent = this_parent->d_parent;
spin_unlock(&dcache_lock);
DPRINTK("parent dentry %p %.*s",
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 2a771ec6695..2241405ffc4 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -143,7 +143,8 @@ static int autofs4_dcache_readdir(struct file * filp, void * dirent, filldir_t f
}
while(1) {
- struct dentry *de = list_entry(list, struct dentry, d_child);
+ struct dentry *de = list_entry(list,
+ struct dentry, d_u.d_child);
if (!d_unhashed(de) && de->d_inode) {
spin_unlock(&dcache_lock);