sched_trace: make buffer size configurable

Large sched_trace buffers cause boot problems on the ARM box. Allow
the user to specify smaller buffers.

1 files changed, 20 insertions, 0 deletions

diff --git a/litmus/Kconfig b/litmus/Kconfig
index 9888589ef126..f1de6fabfc17 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -108,6 +108,26 @@ config SCHED_TASK_TRACE
           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