Merge branch 'fman-next' of git://git.freescale.com/ppc/upstream/linux

[cascardo/linux.git] / kernel / trace / Kconfig

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index ba33267..2a96b06 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -216,6 +216,41 @@ config SCHED_TRACER
          This tracer tracks the latency of the highest priority task
          to be scheduled in, starting from the point it has woken up.
 
          This tracer tracks the latency of the highest priority task
          to be scheduled in, starting from the point it has woken up.
 

+config HWLAT_TRACER
+       bool "Tracer to detect hardware latencies (like SMIs)"
+       select GENERIC_TRACER
+       help
+        This tracer, when enabled will create one or more kernel threads,
+        depening on what the cpumask file is set to, which each thread
+        spinning in a loop looking for interruptions caused by
+        something other than the kernel. For example, if a
+        System Management Interrupt (SMI) takes a noticeable amount of
+        time, this tracer will detect it. This is useful for testing
+        if a system is reliable for Real Time tasks.
+
+        Some files are created in the tracing directory when this
+        is enabled:
+
+          hwlat_detector/width   - time in usecs for how long to spin for
+          hwlat_detector/window  - time in usecs between the start of each
+                                    iteration
+
+        A kernel thread is created that will spin with interrupts disabled
+        for "width" microseconds in every "widow" cycle. It will not spin
+        for "window - width" microseconds, where the system can
+        continue to operate.
+
+        The output will appear in the trace and trace_pipe files.
+
+        When the tracer is not running, it has no affect on the system,
+        but when it is running, it can cause the system to be
+        periodically non responsive. Do not run this tracer on a
+        production system.
+
+        To enable this tracer, echo in "hwlat" into the current_tracer
+        file. Every time a latency is greater than tracing_thresh, it will
+        be recorded into the ring buffer.
+

 config ENABLE_DEFAULT_TRACERS
        bool "Trace process context switches and events"
        depends on !GENERIC_TRACER
 config ENABLE_DEFAULT_TRACERS
        bool "Trace process context switches and events"
        depends on !GENERIC_TRACER