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tracing: Have hwlat trace migrate across tracing_cpumask CPUs

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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>
This commit is contained in:
Steven Rostedt (Red Hat)
2016-07-15 15:48:56 -04:00
committed by Steven Rostedt
parent c850ed38db
commit 0330f7aa8e
2 changed files with 61 additions and 0 deletions
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6
Documentation/trace/hwlat_detector.txt
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@@ -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.