diff options
| author | Ming Lei <tom.leiming@gmail.com> | 2009-07-22 22:48:09 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-08-02 15:41:37 +0200 |
| commit | e351b660fddd4df76cc4635f896d311ed0ff3752 (patch) | |
| tree | 380a67c875a4454bd47a8ce6ddd159432863646e | |
| parent | bb97a91e2549a7f2df9c21d32542582f549ab3ec (diff) | |
lockdep: Reintroduce generation count to make BFS faster
We still can apply DaveM's generation count optimization to
BFS, based on the following idea:
- before doing each BFS, increase the global generation id
by 1
- if one node in the graph has been visited, mark it as
visited by storing the current global generation id into
the node's dep_gen_id field
- so we can decide if one node has been visited already, by
comparing the node's dep_gen_id with the global generation id.
By applying DaveM's generation count optimization to current
implementation of BFS, we gain the following advantages:
- we save MAX_LOCKDEP_ENTRIES/8 bytes memory;
- we remove the bitmap_zero(bfs_accessed, MAX_LOCKDEP_ENTRIES);
in each BFS, which is very time-consuming since
MAX_LOCKDEP_ENTRIES may be very large.(16384UL)
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "David S. Miller" <davem@davemloft.net>
LKML-Reference: <1248274089-6358-1-git-send-email-tom.leiming@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | include/linux/lockdep.h | 1 | ||||
| -rw-r--r-- | kernel/lockdep.c | 11 |
2 files changed, 7 insertions, 5 deletions
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 47d42eff6124..9ccf0e286b2a 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -58,6 +58,7 @@ struct lock_class { struct lockdep_subclass_key *key; unsigned int subclass; + unsigned int dep_gen_id; /* * IRQ/softirq usage tracking bits: diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 0bb246e21cd7..2b443b5090a1 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -861,14 +861,15 @@ struct circular_queue { }; static struct circular_queue lock_cq; -static unsigned long bfs_accessed[BITS_TO_LONGS(MAX_LOCKDEP_ENTRIES)]; unsigned int max_bfs_queue_depth; +static unsigned int lockdep_dependency_gen_id; + static inline void __cq_init(struct circular_queue *cq) { cq->front = cq->rear = 0; - bitmap_zero(bfs_accessed, MAX_LOCKDEP_ENTRIES); + lockdep_dependency_gen_id++; } static inline int __cq_empty(struct circular_queue *cq) @@ -914,7 +915,7 @@ static inline void mark_lock_accessed(struct lock_list *lock, nr = lock - list_entries; WARN_ON(nr >= nr_list_entries); lock->parent = parent; - set_bit(nr, bfs_accessed); + lock->class->dep_gen_id = lockdep_dependency_gen_id; } static inline unsigned long lock_accessed(struct lock_list *lock) @@ -923,7 +924,7 @@ static inline unsigned long lock_accessed(struct lock_list *lock) nr = lock - list_entries; WARN_ON(nr >= nr_list_entries); - return test_bit(nr, bfs_accessed); + return lock->class->dep_gen_id == lockdep_dependency_gen_id; } static inline struct lock_list *get_lock_parent(struct lock_list *child) @@ -3604,7 +3605,7 @@ void __init lockdep_info(void) sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS + sizeof(struct list_head) * CHAINHASH_SIZE) / 1024 #ifdef CONFIG_PROVE_LOCKING - + sizeof(struct circular_queue) + sizeof(bfs_accessed) + + sizeof(struct circular_queue) #endif ); |