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Diffstat (limited to 'Documentation/trace/hwlat_detector.rst')
| -rw-r--r-- | Documentation/trace/hwlat_detector.rst | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/Documentation/trace/hwlat_detector.rst b/Documentation/trace/hwlat_detector.rst index 5739349649c8..11b749c2a8bd 100644 --- a/Documentation/trace/hwlat_detector.rst +++ b/Documentation/trace/hwlat_detector.rst @@ -14,7 +14,7 @@ originally written for use by the "RT" patch since the Real Time kernel is highly latency sensitive. SMIs are not serviced by the Linux kernel, which means that it does not -even know that they are occuring. SMIs are instead set up by BIOS code +even know that they are occurring. SMIs are instead set up by BIOS code and are serviced by BIOS code, usually for "critical" events such as management of thermal sensors and fans. Sometimes though, SMIs are used for other tasks and those tasks can spend an inordinate amount of time in the @@ -76,8 +76,13 @@ in /sys/kernel/tracing: - 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) + - hwlat_detector/mode - the thread mode -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. +By default, one hwlat detector's kernel thread will migrate across each CPU +specified in cpumask at the beginning of a new window, in a round-robin +fashion. This behavior can be changed by changing the thread mode, +the available options are: + + - none: do not force migration + - round-robin: migrate across each CPU specified in cpumask [default] + - per-cpu: create one thread for each cpu in tracing_cpumask |