Re: [PATCH] reduce sizeof(struct file)
From: Eric Dumazet
Date: Fri Sep 23 2005 - 22:43:46 EST
Christoph Hellwig a écrit :
Please just change all callers to use the union, there's not very many
of them.
Yes it's better, thanks Christoph.
What about this version then ?
Hi all
Now that RCU applied on 'struct file' seems stable, we can place f_rcuhead in
a memory location that is not anymore used at call_rcu(&f->f_rcuhead,
file_free_rcu) time, to reduce the size of this critical kernel object.
The trick I used is to move f_rcuhead and f_list in an union called f_u
The callers are changed so that f_rcuhead becomes f_u.fu_rcuhead and f_list
becomes f_u.f_list
Tested on allyesconfig, diffed against 2.6.14-rc2
drivers/char/tty_io.c | 2 +-
fs/dquot.c | 2 +-
fs/file_table.c | 14 +++++++-------
fs/proc/generic.c | 2 +-
fs/super.c | 2 +-
include/linux/fs.h | 9 +++++++--
security/selinux/hooks.c | 2 +-
security/selinux/selinuxfs.c | 2 +-
8 files changed, 20 insertions(+), 15 deletions(-)
Thank you
Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
--- linux-2.6.14-rc2-orig/include/linux/fs.h 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/include/linux/fs.h 2005-09-24 04:52:20.000000000 +0200
@@ -574,7 +574,13 @@
#define RA_FLAG_INCACHE 0x02 /* file is already in cache */
struct file {
- struct list_head f_list;
+/*
+ * f_list and f_rcuhead can share the same memory location
+ */
+ union {
+ struct list_head fu_list;
+ struct rcu_head fu_rcuhead;
+ } f_u;
struct dentry *f_dentry;
struct vfsmount *f_vfsmnt;
struct file_operations *f_op;
@@ -598,7 +604,6 @@
spinlock_t f_ep_lock;
#endif /* #ifdef CONFIG_EPOLL */
struct address_space *f_mapping;
- struct rcu_head f_rcuhead;
};
extern spinlock_t files_lock;
#define file_list_lock() spin_lock(&files_lock);
--- linux-2.6.14-rc2-orig/fs/file_table.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/fs/file_table.c 2005-09-24 05:02:35.000000000 +0200
@@ -56,13 +56,13 @@
static inline void file_free_rcu(struct rcu_head *head)
{
- struct file *f = container_of(head, struct file, f_rcuhead);
+ struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
kmem_cache_free(filp_cachep, f);
}
static inline void file_free(struct file *f)
{
- call_rcu(&f->f_rcuhead, file_free_rcu);
+ call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
}
/* Find an unused file structure and return a pointer to it.
@@ -95,7 +95,7 @@
f->f_gid = current->fsgid;
rwlock_init(&f->f_owner.lock);
/* f->f_version: 0 */
- INIT_LIST_HEAD(&f->f_list);
+ INIT_LIST_HEAD(&f->f_u.fu_list);
return f;
over:
@@ -225,15 +225,15 @@
if (!list)
return;
file_list_lock();
- list_move(&file->f_list, list);
+ list_move(&file->f_u.fu_list, list);
file_list_unlock();
}
void file_kill(struct file *file)
{
- if (!list_empty(&file->f_list)) {
+ if (!list_empty(&file->f_u.fu_list)) {
file_list_lock();
- list_del_init(&file->f_list);
+ list_del_init(&file->f_u.fu_list);
file_list_unlock();
}
}
@@ -245,7 +245,7 @@
/* Check that no files are currently opened for writing. */
file_list_lock();
list_for_each(p, &sb->s_files) {
- struct file *file = list_entry(p, struct file, f_list);
+ struct file *file = list_entry(p, struct file, f_u.fu_list);
struct inode *inode = file->f_dentry->d_inode;
/* File with pending delete? */
--- linux-2.6.14-rc2-orig/drivers/char/tty_io.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/drivers/char/tty_io.c 2005-09-24 05:02:35.000000000 +0200
@@ -809,7 +809,7 @@
check_tty_count(tty, "do_tty_hangup");
file_list_lock();
/* This breaks for file handles being sent over AF_UNIX sockets ? */
- list_for_each_entry(filp, &tty->tty_files, f_list) {
+ list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
if (filp->f_op->write == redirected_tty_write)
cons_filp = filp;
if (filp->f_op->write != tty_write)
--- linux-2.6.14-rc2-orig/fs/dquot.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/fs/dquot.c 2005-09-24 05:02:35.000000000 +0200
@@ -662,7 +662,7 @@
restart:
file_list_lock();
list_for_each(p, &sb->s_files) {
- struct file *filp = list_entry(p, struct file, f_list);
+ struct file *filp = list_entry(p, struct file, f_u.fu_list);
struct inode *inode = filp->f_dentry->d_inode;
if (filp->f_mode & FMODE_WRITE && dqinit_needed(inode, type)) {
struct dentry *dentry = dget(filp->f_dentry);
--- linux-2.6.14-rc2-orig/fs/proc/generic.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/fs/proc/generic.c 2005-09-24 05:02:35.000000000 +0200
@@ -533,7 +533,7 @@
*/
file_list_lock();
list_for_each(p, &sb->s_files) {
- struct file * filp = list_entry(p, struct file, f_list);
+ struct file * filp = list_entry(p, struct file, f_u.fu_list);
struct dentry * dentry = filp->f_dentry;
struct inode * inode;
struct file_operations *fops;
--- linux-2.6.14-rc2-orig/fs/super.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/fs/super.c 2005-09-24 05:02:35.000000000 +0200
@@ -513,7 +513,7 @@
struct file *f;
file_list_lock();
- list_for_each_entry(f, &sb->s_files, f_list) {
+ list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
f->f_mode &= ~FMODE_WRITE;
}
--- linux-2.6.14-rc2-orig/security/selinux/hooks.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/security/selinux/hooks.c 2005-09-24 05:02:35.000000000 +0200
@@ -1599,7 +1599,7 @@
if (tty) {
file_list_lock();
- file = list_entry(tty->tty_files.next, typeof(*file), f_list);
+ file = list_entry(tty->tty_files.next, typeof(*file), f_u.fu_list);
if (file) {
/* Revalidate access to controlling tty.
Use inode_has_perm on the tty inode directly rather
--- linux-2.6.14-rc2-orig/security/selinux/selinuxfs.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2/security/selinux/selinuxfs.c 2005-09-24 05:02:35.000000000 +0200
@@ -924,7 +924,7 @@
file_list_lock();
list_for_each(p, &sb->s_files) {
- struct file * filp = list_entry(p, struct file, f_list);
+ struct file * filp = list_entry(p, struct file, f_u.fu_list);
struct dentry * dentry = filp->f_dentry;
if (dentry->d_parent != de) {