Add schedule tracing support

This patch introduces the sched_trace infrastructure, which in
principle allows tracing the generated schedule.  However, this patch
does not yet integrate the callbacks with the kernel.

1 files changed, 34 insertions, 0 deletions

diff --git a/litmus/Kconfig b/litmus/Kconfig
index e4624ee20adc..19211ac1320a 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -24,6 +24,40 @@ config FEATHER_TRACE
           you still need to enable SCHED_TASK_TRACE and/or SCHED_OVERHEAD_TRACE to
           actually enable any events.
 
+config SCHED_TASK_TRACE
+        bool "Trace real-time tasks"
+        depends on FEATHER_TRACE
+        default y
+        help
+          Include support for the sched_trace_XXX() tracing functions. This
+          allows the collection of real-time task events such as job
+          completions, job releases, early completions, etc. This results in  a
+          small overhead in the scheduling code. Disable if the overhead is not
+          acceptable (e.g., benchmarking).
+
+          Say Yes for debugging.
+          Say No for overhead tracing.
+
+config SCHED_TASK_TRACE_SHIFT
+       int "Buffer size for sched_trace_xxx() events"
+       depends on SCHED_TASK_TRACE
+       range 8 13
+       default 9
+       help
+
+         Select the buffer size of sched_trace_xxx() events as a power of two.
+         These buffers are statically allocated as per-CPU data. Each event
+         requires 24 bytes storage plus one additional flag byte. Too large
+         buffers can cause issues with the per-cpu allocator (and waste
+         memory). Too small buffers can cause scheduling events to be lost. The
+         "right" size is workload dependent and depends on the number of tasks,
+         each task's period, each task's number of suspensions, and how often
+         the buffer is flushed.
+
+         Examples: 12 =>   4k events
+                   10 =>   1k events
+                    8 =>  512 events
+
 config SCHED_OVERHEAD_TRACE
         bool "Record timestamps for overhead measurements"
         depends on FEATHER_TRACE