On Fri, May 31, 2013 at 11:07:31PM -0400, Jeff Layton wrote:
> Testing has shown that iterating over the blocked_list for deadlock
> detection turns out to be a bottleneck. In order to alleviate that,
> begin the process of turning it into a hashtable. We start by turning
> the fl_link into a hlist_node and the global lists into hlists. A later
> patch will do the conversion of the blocked_list to a hashtable.
Even simpler would be if we could add a pointer to the (well, a) lock
that a lockowner is blocking on, and then we'd just have to follow a
pointer. I haven't thought that through, though, perhaps that's hard ot
make work....
--b.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/locks.c | 32 ++++++++++++++++----------------
> include/linux/fs.h | 2 +-
> 2 files changed, 17 insertions(+), 17 deletions(-)
>
> diff --git a/fs/locks.c b/fs/locks.c
> index fc35b9e..5ed056b 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -163,8 +163,8 @@ int lease_break_time = 45;
> #define for_each_lock(inode, lockp) \
> for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
>
> -static LIST_HEAD(file_lock_list);
> -static LIST_HEAD(blocked_list);
> +static HLIST_HEAD(file_lock_list);
> +static HLIST_HEAD(blocked_list);
>
> /* Protects the two list heads above */
> static DEFINE_SPINLOCK(file_lock_lock);
> @@ -173,7 +173,7 @@ static struct kmem_cache *filelock_cache __read_mostly;
>
> static void locks_init_lock_heads(struct file_lock *fl)
> {
> - INIT_LIST_HEAD(&fl->fl_link);
> + INIT_HLIST_NODE(&fl->fl_link);
> INIT_LIST_HEAD(&fl->fl_block);
> init_waitqueue_head(&fl->fl_wait);
> }
> @@ -207,7 +207,7 @@ void locks_free_lock(struct file_lock *fl)
> {
> BUG_ON(waitqueue_active(&fl->fl_wait));
> BUG_ON(!list_empty(&fl->fl_block));
> - BUG_ON(!list_empty(&fl->fl_link));
> + BUG_ON(!hlist_unhashed(&fl->fl_link));
>
> locks_release_private(fl);
> kmem_cache_free(filelock_cache, fl);
> @@ -486,7 +486,7 @@ static inline void
> locks_insert_global_blocked(struct file_lock *waiter)
> {
> spin_lock(&file_lock_lock);
> - list_add(&waiter->fl_link, &blocked_list);
> + hlist_add_head(&waiter->fl_link, &blocked_list);
> spin_unlock(&file_lock_lock);
> }
>
> @@ -494,7 +494,7 @@ static inline void
> locks_delete_global_blocked(struct file_lock *waiter)
> {
> spin_lock(&file_lock_lock);
> - list_del_init(&waiter->fl_link);
> + hlist_del_init(&waiter->fl_link);
> spin_unlock(&file_lock_lock);
> }
>
> @@ -502,7 +502,7 @@ static inline void
> locks_insert_global_locks(struct file_lock *waiter)
> {
> spin_lock(&file_lock_lock);
> - list_add_tail(&waiter->fl_link, &file_lock_list);
> + hlist_add_head(&waiter->fl_link, &file_lock_list);
> spin_unlock(&file_lock_lock);
> }
>
> @@ -510,7 +510,7 @@ static inline void
> locks_delete_global_locks(struct file_lock *waiter)
> {
> spin_lock(&file_lock_lock);
> - list_del_init(&waiter->fl_link);
> + hlist_del_init(&waiter->fl_link);
> spin_unlock(&file_lock_lock);
> }
>
> @@ -705,7 +705,7 @@ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
> {
> struct file_lock *fl, *ret = NULL;
>
> - list_for_each_entry(fl, &blocked_list, fl_link) {
> + hlist_for_each_entry(fl, &blocked_list, fl_link) {
> if (posix_same_owner(fl, block_fl)) {
> ret = fl->fl_next;
> if (likely(ret))
> @@ -867,7 +867,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
> goto out;
> error = FILE_LOCK_DEFERRED;
> locks_insert_block(fl, request);
> - if (list_empty(&request->fl_link))
> + if (hlist_unhashed(&request->fl_link))
> locks_insert_global_blocked(request);
> goto out;
> }
> @@ -882,10 +882,10 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
> * Now that we know the request is no longer blocked, we can take it
> * off the global list. Some callers send down partially initialized
> * requests, so we only do this if FL_SLEEP is set. Also, avoid taking
> - * the lock if the list is empty, as that indicates a request that
> + * the lock if the hlist is unhashed, as that indicates a request that
> * never blocked.
> */
> - if ((request->fl_flags & FL_SLEEP) && !list_empty(&request->fl_link))
> + if ((request->fl_flags & FL_SLEEP) && !hlist_unhashed(&request->fl_link))
> locks_delete_global_blocked(request);
>
> /*
> @@ -2277,11 +2277,11 @@ static int locks_show(struct seq_file *f, void *v)
> {
> struct file_lock *fl, *bfl;
>
> - fl = list_entry(v, struct file_lock, fl_link);
> + fl = hlist_entry(v, struct file_lock, fl_link);
>
> lock_get_status(f, fl, *((loff_t *)f->private), "");
>
> - list_for_each_entry(bfl, &blocked_list, fl_link) {
> + hlist_for_each_entry(bfl, &blocked_list, fl_link) {
> if (bfl->fl_next == fl)
> lock_get_status(f, bfl, *((loff_t *)f->private), " ->");
> }
> @@ -2295,14 +2295,14 @@ static void *locks_start(struct seq_file *f, loff_t *pos)
>
> spin_lock(&file_lock_lock);
> *p = (*pos + 1);
> - return seq_list_start(&file_lock_list, *pos);
> + return seq_hlist_start(&file_lock_list, *pos);
> }
>
> static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
> {
> loff_t *p = f->private;
> ++*p;
> - return seq_list_next(v, &file_lock_list, pos);
> + return seq_hlist_next(v, &file_lock_list, pos);
> }
>
> static void locks_stop(struct seq_file *f, void *v)
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index ccb44ea..07a009e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -934,7 +934,7 @@ int locks_in_grace(struct net *);
> */
> struct file_lock {
> struct file_lock *fl_next; /* singly linked list for this inode */
> - struct list_head fl_link; /* doubly linked list of all locks */
> + struct hlist_node fl_link; /* node in global lists */
> struct list_head fl_block; /* circular list of blocked processes */
> fl_owner_t fl_owner;
> unsigned int fl_flags;
> --
> 1.7.1
>
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