Commit-ID: 68e9dc29f8f42c79d2a3755223ed910ce36b4ae2 Gitweb: https://git.kernel.org/tip/68e9dc29f8f42c79d2a3755223ed910ce36b4ae2 Author: Yuyang Du <duyuyang@xxxxxxxxx> AuthorDate: Mon, 6 May 2019 16:19:36 +0800 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Mon, 3 Jun 2019 11:55:50 +0200 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@xxxxxxxxxxxxx> Signed-off-by: Yuyang Du <duyuyang@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: bvanassche@xxxxxxx Cc: frederic@xxxxxxxxxx Cc: ming.lei@xxxxxxxxxx Cc: will.deacon@xxxxxxx Link: https://lkml.kernel.org/r/20190506081939.74287-21-duyuyang@xxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/locking/lockdep.c | 4 ++++ 1 file changed, 4 insertions(+) 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;
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