From bb5e4454fee1e01d4c18b27e957a6f759e3f0880 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Mon, 16 Sep 2024 21:41:52 +0200
Subject: [PATCH] putil: Add debug for oversleeping/undersleeping with
 M_limited clock

---
 panda/src/putil/clockObject.cxx  | 16 ++++++++++++++++
 panda/src/putil/config_putil.cxx |  6 +++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/panda/src/putil/clockObject.cxx b/panda/src/putil/clockObject.cxx
index 8fa128616f..1add57a6e1 100644
--- a/panda/src/putil/clockObject.cxx
+++ b/panda/src/putil/clockObject.cxx
@@ -499,6 +499,8 @@ wait_until(double want_time) {
 
   double wait_interval = (want_time - _actual_frame_time) - sleep_precision;
 
+  double now = get_real_time();
+
   if (wait_interval > 0.0) {
     Thread::sleep(wait_interval);
   }
@@ -507,6 +509,20 @@ wait_until(double want_time) {
   (*_start_clock_busy_wait)();
 #endif
 
+  _actual_frame_time = get_real_time();
+  if (_actual_frame_time > want_time) {
+    if (util_cat.is_debug()) {
+      util_cat.debug()
+        << "Overslept by " << (int)((_actual_frame_time - want_time) * 1000000)
+        << " us while waiting for next frame, consider raising sleep-precision.\n";
+    }
+  }
+  else if (util_cat.is_spam()) {
+    util_cat.spam()
+      << "Busy waiting for " << (int)((want_time - _actual_frame_time) * 1000000)
+      << " us.\n";
+  }
+
   // Now busy-wait until the actual time elapses.
   while (_actual_frame_time < want_time) {
     _actual_frame_time = get_real_time();
diff --git a/panda/src/putil/config_putil.cxx b/panda/src/putil/config_putil.cxx
index 93694b3d30..9849cd5b84 100644
--- a/panda/src/putil/config_putil.cxx
+++ b/panda/src/putil/config_putil.cxx
@@ -129,9 +129,9 @@ get_plugin_path() {
 
 ConfigVariableDouble sleep_precision
 ("sleep-precision", 0.01,
- PRC_DESC("This is the accuracy within which we can expect select() to "
-          "return precisely.  That is, if we use select() to request a "
-          "timeout of 1.0 seconds, we can expect to actually sleep for "
+ PRC_DESC("This is the accuracy within which we can expect the operating "
+          "system sleep call to return precisely.  That is, if we request "
+          "a timeout of 1.0 seconds, we can expect to actually sleep for "
           "somewhere between 1.0 and 1.0 + sleep-precision seconds."));
 
 ConfigVariableBool preload_textures