From 5020d33748e14cfc4c2a4a5254a07864095af49e Mon Sep 17 00:00:00 2001
From: whoisdomi <dcantu83@gmail.com>
Date: Fri, 29 May 2026 08:33:16 -0500
Subject: [PATCH] ui+selfdrived: pin UI after init, move selfdrived to core 5

Move the UI core-affinity pin to after MainWindow init so startup and
restart recovery can use all cores (pinning before init starved the
restarting UI on the contended little cores, stretching recovery from
~30s to minutes). Move selfdrived off the saturated core 4 onto core 5
so its 100 Hz loop is no longer starved, eliminating selfdrivedLagging.

Verified over a full drive: selfdrivedLagging=0, core4/core5 sustained
>=95% only 0.3%/1.2% of the time, UI restart recovery ~15s with the
device staying engaged, radar tracking unaffected.
---
 selfdrive/selfdrived/selfdrived.py |  7 ++++++-
 selfdrive/ui/main.cc               | 21 ++++++++++++---------
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/selfdrive/selfdrived/selfdrived.py b/selfdrive/selfdrived/selfdrived.py
index 200efa9155..1bdadf0474 100644
--- a/selfdrive/selfdrived/selfdrived.py
+++ b/selfdrive/selfdrived/selfdrived.py
@@ -721,7 +721,12 @@ class SelfdriveD:
 
 
 def main():
-  config_realtime_process(4, Priority.CTRL_HIGH)
+  # Run on core 5 (plannerd/radard, ~50% peak, FIFO prio 51) instead of sharing
+  # the saturated core 4 with card+controlsd. Core 4 at 100% was starving
+  # selfdrived's 100 Hz loop and firing selfdrivedLagging. selfdrived's higher
+  # FIFO prio (53 > 51) lets it preempt the 20 Hz planner/radar when needed.
+  # (Core 6 = camerad, core 7 = modeld are both timing-critical — avoid.)
+  config_realtime_process(5, Priority.CTRL_HIGH)
   s = SelfdriveD()
   s.run()
 
diff --git a/selfdrive/ui/main.cc b/selfdrive/ui/main.cc
index 35ee73528f..9c11032116 100644
--- a/selfdrive/ui/main.cc
+++ b/selfdrive/ui/main.cc
@@ -31,15 +31,6 @@ void waylandAwareMessageHandler(QtMsgType type, const QMessageLogContext &contex
 int main(int argc, char *argv[]) {
   setpriority(PRIO_PROCESS, 0, -20);
 
-  // Pin the UI to the little cores (0-3). The realtime control loop
-  // (card/controlsd/selfdrived) runs SCHED_FIFO on core 4; without this pin the
-  // kernel can schedule the UI there, and a UI stall/restart spike preempts
-  // selfdrived, starving its 100 Hz loop and firing the "System Lagging" alert.
-  // Set before any threads spawn so children inherit the affinity.
-  if (!Hardware::PC()) {
-    util::set_core_affinity({0, 1, 2, 3});
-  }
-
   qInstallMessageHandler(waylandAwareMessageHandler);
   initApp(argc, argv);
 
@@ -55,5 +46,17 @@ int main(int argc, char *argv[]) {
   MainWindow w;
   setMainWindow(&w);
   a.installEventFilter(&w);
+
+  // Pin the UI to the little cores (0-3) AFTER startup. The realtime control
+  // loop (card/controlsd) runs SCHED_FIFO on core 4; this keeps the steady-state
+  // UI off it so a UI stall can't preempt the control loop. Deliberately done
+  // after MainWindow init so startup — and crucially restart recovery — can use
+  // all cores; pinning before init starved the restarting UI on the contended
+  // little cores and stretched recovery from ~30s to minutes. The per-second
+  // reaffine in UIState::update keeps it pinned thereafter.
+  if (!Hardware::PC()) {
+    util::set_core_affinity({0, 1, 2, 3});
+  }
+
   return a.exec();
 }