From 43b4578071c0e6d87761e113e05d45776cc75437 Mon Sep 17 00:00:00 2001 From: Andrew Hunter Date: Thu, 23 May 2013 11:07:03 -0700 Subject: perf/x86: Reduce stack usage of x86_schedule_events() x86_schedule_events() caches event constraints on the stack during scheduling. Given the number of possible events, this is 512 bytes of stack; since it can be invoked under schedule() under god-knows-what, this is causing stack blowouts. Trade some space usage for stack safety: add a place to cache the constraint pointer to struct perf_event. For 8 bytes per event (1% of its size) we can save the giant stack frame. This shouldn't change any aspect of scheduling whatsoever and while in theory the locality's a tiny bit worse, I doubt we'll see any performance impact either. Tested: `perf stat whatever` does not blow up and produces results that aren't hugely obviously wrong. I'm not sure how to run particularly good tests of perf code, but this should not produce any functional change whatsoever. Signed-off-by: Andrew Hunter Reviewed-by: Stephane Eranian Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1369332423-4400-1-git-send-email-ahh@google.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/perf_event.h') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 4bc57d017fc8..33e8d65836d6 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -113,6 +113,8 @@ struct hw_perf_event_extra { int idx; /* index in shared_regs->regs[] */ }; +struct event_constraint; + /** * struct hw_perf_event - performance event hardware details: */ @@ -131,6 +133,8 @@ struct hw_perf_event { struct hw_perf_event_extra extra_reg; struct hw_perf_event_extra branch_reg; + + struct event_constraint *constraint; }; struct { /* software */ struct hrtimer hrtimer; -- cgit v1.2.1