[PATCH 3/9] rteval: Update config files to clarify measurement module selection

Add explicit [measurement] section with documentation to both config
files to clarify that timerlat is the default measurement module.

1. Add [measurement] section to rteval.conf (root directory)
   - This file gets installed to /etc/rteval.conf
   - Document that timerlat is the default (SCHED_DEADLINE based)
   - Document cyclictest as legacy alternative (SCHED_FIFO based)
   - Show how to change the measurement module

2. Add [measurement] section to rteval/rteval.conf (subdirectory)
   - Used by development builds and Makefile targets
   - Same documentation as root config for consistency
   - Previously lacked this section entirely

The presence of [cyclictest] and [timerlat] configuration sections in
the config files created confusion about which module is actually used.
Without an explicit [measurement] section, rteval defaults to timerlat,
but this was not documented in the config files.

Assisted-by: Claude Sonnet 4.5 <[email protected]>
Signed-off-by: John Kacur <[email protected]>
---
 rteval.conf        |  5 ++++-
 rteval/rteval.conf | 12 ++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/rteval.conf b/rteval.conf
index 46a9b1743716..fdb64abe8797 100644
--- a/rteval.conf
+++ b/rteval.conf
@@ -5,9 +5,12 @@
 duration:  60.0
 report_interval: 600
 
+# Measurement module selection
+# Default: timerlat (preferred for modern kernels with SCHED_DEADLINE support)
+# Alternative: cyclictest (legacy, SCHED_FIFO based)
 [measurement]
-# cyclictest: module
 timerlat: module
+# cyclictest: module
 
 [loads]
 kcompile:  module
diff --git a/rteval/rteval.conf b/rteval/rteval.conf
index e4437e04347a..87c0ba45921f 100644
--- a/rteval/rteval.conf
+++ b/rteval/rteval.conf
@@ -5,12 +5,24 @@ debugging: False
 duration:  60.0
 report_interval: 600
 
+# Measurement module selection
+# Default: timerlat (preferred for modern kernels with SCHED_DEADLINE support)
+# Alternative: cyclictest (legacy, SCHED_FIFO based)
+# To change, set one of: timerlat: module OR cyclictest: module
+[measurement]
+timerlat: module
+
 [cyclictest]
 buckets:	3500
 interval:	100
 distance:	0
 priority:	95
 
+[timerlat]
+buckets:	3500
+interval:	100
+priority:	95
+
 [loads]
 kcompile:  module
 hackbench: module
-- 
2.54.0