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>
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 47d42ef..9ccf0e2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -58,6 +58,7 @@
struct lockdep_subclass_key *key;
unsigned int subclass;
+ unsigned int dep_gen_id;
/*
* IRQ/softirq usage tracking bits: