From d0618410eced4eb092295fad10312a4545fcdfaf Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Tue, 22 Aug 2017 19:22:43 +0200 Subject: tracing, perf: Adjust code layout in get_recursion_context() In an XDP redirect applications using tracepoint xdp:xdp_redirect to diagnose TX overrun, I noticed perf_swevent_get_recursion_context() was consuming 2% CPU. This was reduced to 1.85% with this simple change. Looking at the annotated asm code, it was clear that the unlikely case in_nmi() test was chosen (by the compiler) as the most likely event/branch. This small adjustment makes the compiler (GCC version 7.1.1 20170622 (Red Hat 7.1.1-3)) put in_nmi() as an unlikely branch. Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/150342256382.16595.986861478681783732.stgit@firesoul Signed-off-by: Ingo Molnar --- kernel/events/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/events') diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 5377c591c57a..843e97047335 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -208,7 +208,7 @@ static inline int get_recursion_context(int *recursion) { int rctx; - if (in_nmi()) + if (unlikely(in_nmi())) rctx = 3; else if (in_irq()) rctx = 2; -- cgit v1.2.3