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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2016-07-15 15:48:56 -0400
committerSteven Rostedt <rostedt@goodmis.org>2016-09-02 12:47:54 -0400
commit0330f7aa8ee63d0c435c0cb4e47ea06235ee4b7f (patch)
tree67fa852b52a5c4c09ec74f6ba38c7b44f14af180 /Documentation/trace
parentc850ed38db5f46441565174ef57c271124cce568 (diff)
downloadlinux-0330f7aa8ee63d0c435c0cb4e47ea06235ee4b7f.tar.bz2
tracing: Have hwlat trace migrate across tracing_cpumask CPUs
Instead of having the hwlat detector thread stay on one CPU, have it migrate across all the CPUs specified by tracing_cpumask. If the user modifies the thread's CPU affinity, the migration will stop until the next instance that the tracer is instantiated. The migration happens at the end of each window (period). Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/hwlat_detector.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/trace/hwlat_detector.txt b/Documentation/trace/hwlat_detector.txt
index c02e8ef800cf..3207717a0d1a 100644
--- a/Documentation/trace/hwlat_detector.txt
+++ b/Documentation/trace/hwlat_detector.txt
@@ -69,5 +69,11 @@ in /sys/kernel/tracing:
tracing_threshold - minimum latency value to be considered (usecs)
tracing_max_latency - maximum hardware latency actually observed (usecs)
+ tracing_cpumask - the CPUs to move the hwlat thread across
hwlat_detector/width - specified amount of time to spin within window (usecs)
hwlat_detector/window - amount of time between (width) runs (usecs)
+
+The hwlat detector's kernel thread will migrate across each CPU specified in
+tracing_cpumask between each window. To limit the migration, either modify
+tracing_cpumask, or modify the hwlat kernel thread (named [hwlatd]) CPU
+affinity directly, and the migration will stop.