rt-app: add log buffer in memory

With the new mechanism that is used to describe a scenario, it becomes more
complex to estimate how many logs will be generated during the execution of a
use case. As a result, the record of the logs in temporary buffer had been
disable and the logs were saved directly in files. The potential side effect
of such mecanism is to block threads on io access, which disturbs the use case
behavior.

A new parameter is added to define the saving policy of the logs. You can
now disable the logs, save them directly in a file like previously,
define the size of a temporary buffer but with the risk to lost some logs if
the buffer overflow. You can also ask rt-app to evaluate how many logs will be
generated and allocate the temporary buffer accordingly. This last mode is not
yet implemented and it will be part of a dedicated patch.

Full details of the new parameter is available in the update of the
documentation

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/tutorial.txt b/doc/tutorial.txt
index 12aba47..8341b2e 100644
--- a/doc/tutorial.txt
+++ b/doc/tutorial.txt
@@ -61,6 +61,20 @@ the current directory (./).
 * log_basename : Text. Prefix used for all log files of the use case.
 "rt-app-" is used by default.
 
+* log_size : String or Integer. A Integer defines a fix size in MB of the
+temporary buffer (size per thread) that will be used to store the log data
+before saving them in a file. This temporary buffer is used as a cicular
+buffer so the oldest data will be lost in case of overflow. A string is used
+to set a predifined behavior:
+  - "file" will be used to store the log data directly in the file without
+	using a temporary buffer.
+  - "Disable" will disable the log mecahnism.
+  - "Auto" will let rt-app compute the buffer size to not overflow the latter 
+	during the use case.
+The use of a temporary buffer prevents the threads of unexpected wait during
+io access. The "Auto" mode is not implemented yet and fallback to "file" mode
+for the moment.
+
 * ftrace: Boolean. If enable, rt-app logs in ftrace the main events of the use
 case. Default value is False.
 
@@ -75,6 +89,7 @@ each threads (see gnuplot section for more details). Default value is False.
 		"pi_enabled" : false,
 		"lock_pages" : false,
 		"logdir" : "./",
+		"log_size" : "file",
 		"log_basename" : "rt-app",
 		"ftrace" : false,
 		"gnuplot" : false,