From f7270c44cb1c4afe570921d711ee124a43c9e69b Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Fri, 11 Mar 2022 15:13:39 +0100
Subject: [PATCH] trace_logger: omit inactive subjects by default

This patch reduces repetitive log output by omitting inactive trace
subjects from the log output. The information about all subjects can
still be dumped by setting 'verbose="yes"'.

Issue #4448
---
 repos/os/include/trace/trace_buffer.h    | 10 ++++++----
 repos/os/src/app/trace_logger/README     |  1 +
 repos/os/src/app/trace_logger/main.cc    |  4 +++-
 repos/os/src/app/trace_logger/monitor.cc | 13 +++++++++----
 repos/os/src/app/trace_logger/monitor.h  |  4 +++-
 5 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/repos/os/include/trace/trace_buffer.h b/repos/os/include/trace/trace_buffer.h
index abf26309ac..13c39e61d6 100644
--- a/repos/os/include/trace/trace_buffer.h
+++ b/repos/os/include/trace/trace_buffer.h
@@ -26,7 +26,7 @@ class Trace_buffer
 	private:
 
 		Genode::Trace::Buffer        &_buffer;
-		Genode::Trace::Buffer::Entry  _curr          { _buffer.first() };
+		Genode::Trace::Buffer::Entry  _curr { _buffer.first() };
 		unsigned long long            _lost_count { 0 };
 
 	public:
@@ -48,7 +48,7 @@ class Trace_buffer
 				_lost_count = (unsigned)_buffer.lost_entries();
 			}
 
-			Trace::Buffer::Entry entry    { _curr };
+			Trace::Buffer::Entry entry { _curr };
 
 			/**
 			 * Iterate over all entries that were not processed yet.
@@ -59,6 +59,7 @@ class Trace_buffer
 			 * if the 'last' end of the buffer (highest address) was reached.
 			 */
 			for (; !entry.head(); entry = _buffer.next(entry)) {
+
 				/* continue at first entry if we hit the end of the buffer */
 				if (entry.last())
 					entry = _buffer.first();
@@ -76,8 +77,9 @@ class Trace_buffer
 			if (update) _curr = entry;
 		}
 
-		void * address()        const { return &_buffer; }
+		void * address() const { return &_buffer; }
+
+		bool empty() const { return _curr.head(); }
 };
 
-
 #endif /* _TRACE__TRACE_BUFFER_H_ */
diff --git a/repos/os/src/app/trace_logger/README b/repos/os/src/app/trace_logger/README
index a800e1bf85..83c8031441 100644
--- a/repos/os/src/app/trace_logger/README
+++ b/repos/os/src/app/trace_logger/README
@@ -36,6 +36,7 @@ This is a short description of the tags and attributes:
 
 :config.verbose:
   Optional. Toggles wether the trace_logger shall log debugging information.
+  If enabled, even inactive trace subjects appear in the log.
 
 :config.session_ram:
   Optional. Amount of RAM donated to the trace session.
diff --git a/repos/os/src/app/trace_logger/main.cc b/repos/os/src/app/trace_logger/main.cc
index b2e550fd3e..1cc9e99938 100644
--- a/repos/os/src/app/trace_logger/main.cc
+++ b/repos/os/src/app/trace_logger/main.cc
@@ -150,7 +150,9 @@ class Main
 			log("");
 			log("--- Report ", _report_id++, " (", _num_monitors, "/", _num_subjects, " subjects) ---");
 			new_monitors.for_each([&] (Monitor &monitor) {
-				monitor.print(_activity, _affinity);
+				monitor.print(Monitor::Level_of_detail { .activity    =  _activity,
+				                                         .affinity    =  _affinity,
+				                                         .active_only = !_verbose });
 			});
 		}
 
diff --git a/repos/os/src/app/trace_logger/monitor.cc b/repos/os/src/app/trace_logger/monitor.cc
index 87ed250869..3db66d518c 100644
--- a/repos/os/src/app/trace_logger/monitor.cc
+++ b/repos/os/src/app/trace_logger/monitor.cc
@@ -86,8 +86,13 @@ void Monitor::update_info(Trace::Subject_info const &info)
 }
 
 
-void Monitor::print(bool activity, bool affinity)
+void Monitor::print(Level_of_detail detail)
 {
+	/* skip output for a subject with no recent activity */
+	bool const inactive = (_recent_exec_time == 0) && _buffer.empty();
+	if (detail.active_only && inactive)
+		return;
+
 	/* print general subject information */
 	typedef Trace::Subject_info Subject_info;
 	Subject_info::State const state = _info.state();
@@ -98,13 +103,13 @@ void Monitor::print(bool activity, bool affinity)
 	          "\">");
 
 	/* print subjects activity if desired */
-	if (activity)
+	if (detail.activity)
 		log("   <activity total=\"",  _info.execution_time().thread_context,
 		              "\" recent=\"", _recent_exec_time,
 		              "\">");
 
 	/* print subjects affinity if desired */
-	if (affinity)
+	if (detail.affinity)
 		log("   <affinity xpos=\"", _info.affinity().xpos(),
 		              "\" ypos=\"", _info.affinity().ypos(),
 		              "\">");
@@ -139,7 +144,7 @@ void Monitor::print(bool activity, bool affinity)
 	if (printed_buf_entries)
 		log("   </buffer>");
 	else
-		log("   <buffer />");
+		log("   <buffer/>");
 	log("</subject>");
 }
 
diff --git a/repos/os/src/app/trace_logger/monitor.h b/repos/os/src/app/trace_logger/monitor.h
index 5c6d9b29b8..bc10e10569 100644
--- a/repos/os/src/app/trace_logger/monitor.h
+++ b/repos/os/src/app/trace_logger/monitor.h
@@ -67,7 +67,9 @@ class Monitor : public Monitor_base,
 		        Genode::Trace::Subject_id          subject_id,
 		        Genode::Trace::Subject_info const &info);
 
-		void print(bool activity, bool affinity);
+		struct Level_of_detail { bool activity, affinity, active_only; };
+
+		void print(Level_of_detail);
 
 
 		/**************