diff options
| author | Yuyang Du <duyuyang@gmail.com> | 2019-05-06 16:19:36 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-06-03 11:55:50 +0200 |
| commit | 68e9dc29f8f42c79d2a3755223ed910ce36b4ae2 (patch) | |
| tree | cb426eeccf7fcd4979f5600316a3086b76d5178a | |
| parent | 8c2c2b449aa50463ba4cc1f33cdfc98750ed03ab (diff) | |
locking/lockdep: Check redundant dependency only when CONFIG_LOCKDEP_SMALL
As Peter has put it all sound and complete for the cause, I simply quote:
"It (check_redundant) was added for cross-release (which has since been
reverted) which would generate a lot of redundant links (IIRC) but
having it makes the reports more convoluted -- basically, if we had an
A-B-C relation, then A-C will not be added to the graph because it is
already covered. This then means any report will include B, even though
a shorter cycle might have been possible."
This would increase the number of direct dependencies. For a simple workload
(make clean; reboot; make vmlinux -j8), the data looks like this:
CONFIG_LOCKDEP_SMALL: direct dependencies: 6926
!CONFIG_LOCKDEP_SMALL: direct dependencies: 9052 (+30.7%)
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Yuyang Du <duyuyang@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-21-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/locking/lockdep.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 30a1c0e32573..63b82921698d 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1739,6 +1739,7 @@ check_noncircular(struct held_lock *src, struct held_lock *target, return ret; } +#ifdef CONFIG_LOCKDEP_SMALL /* * Check that the dependency graph starting at <src> can lead to * <target> or not. If it can, <src> -> <target> dependency is already @@ -1768,6 +1769,7 @@ check_redundant(struct held_lock *src, struct held_lock *target) return ret; } +#endif #ifdef CONFIG_TRACE_IRQFLAGS @@ -2428,12 +2430,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, } } +#ifdef CONFIG_LOCKDEP_SMALL /* * Is the <prev> -> <next> link redundant? */ ret = check_redundant(prev, next); if (ret != 1) return ret; +#endif if (!trace->nr_entries && !save_trace(trace)) return 0; |