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| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2017-08-22 19:22:43 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-08-25 11:04:18 +0200 |
| commit | d0618410eced4eb092295fad10312a4545fcdfaf (patch) | |
| tree | 927f02a812f22f476c608dabcd4e6b25917963ff /kernel/events | |
| parent | 1d953111b648e48923171c3c9cf17be2250544fa (diff) | |
| download | linux-d0618410eced4eb092295fad10312a4545fcdfaf.tar.bz2 | |
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 <brouer@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/150342256382.16595.986861478681783732.stgit@firesoul
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/internal.h | 2 |
1 files changed, 1 insertions, 1 deletions
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; |