| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 89/92] tracing/hwlat: Dont ignore outer-loop duration when calculating max_latency | Date | Wed, 16 Oct 2019 14:51:02 -0700 |
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From: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
commit fc64e4ad80d4b72efce116f87b3174f0b7196f8e upstream.
max_latency is intended to record the maximum ever observed hardware latency, which may occur in either part of the loop (inner/outer). So we need to also consider the outer-loop sample when updating max_latency.
Link: http://lkml.kernel.org/r/157073345463.17189.18124025522664682811.stgit@srivatsa-ubuntu
Fixes: e7c15cd8a113 ("tracing: Added hardware latency tracer") Cc: stable@vger.kernel.org Signed-off-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/trace/trace_hwlat.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -257,6 +257,8 @@ static int get_sample(void) /* Keep a running maximum ever recorded hardware latency */ if (sample > tr->max_latency) tr->max_latency = sample; + if (outer_sample > tr->max_latency) + tr->max_latency = outer_sample; } out:
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