commit 5db29f25e45edb810b9cc3f05a9d58d393f3e619
author Austin Schuh <austin.linux@gmail.com> Sat Mar 16 17:00:31 2024 -0700
committer Austin Schuh <austin.linux@gmail.com> Sat Mar 16 17:18:44 2024 -0700
tree fdee6b0ef4ca52af7dc3132b13ad9f2a06d9c11e
parent 2b56ff3c8e1e4a31b4c755c55371e7436bc15551

Prioritize nvargus-daemon and other threads

A large part of our critical path work in libargus was running at
SCHED_OTHER.  Move this to SCHED_FIFO so it will run.  This reduces
outliers to down in the 8ms from 16+.

Change-Id: Ib86a07f70f3715328b86d83ee91aada4ab441cd7
Signed-off-by: Austin Schuh <austin.linux@gmail.com>

frc971/orin/argus_camera.cc

diff --git a/frc971/orin/argus_camera.cc b/frc971/orin/argus_camera.cc
index 62ae36e..42686a1 100644
--- a/frc971/orin/argus_camera.cc
+++ b/frc971/orin/argus_camera.cc
@@ -1,3 +1,5 @@
+#include <dirent.h>
+
 #include <chrono>
 #include <filesystem>
 #include <thread>
@@ -631,6 +633,25 @@
 
     camera.Start();
 
+    // Set the libargus threads which got spawned to RT priority.
+    {
+      DIR *dirp = opendir("/proc/self/task");
+      PCHECK(dirp != nullptr);
+      const int main_pid = getpid();
+      struct dirent *directory_entry;
+      while ((directory_entry = readdir(dirp)) != NULL) {
+        const int thread_id = std::atoi(directory_entry->d_name);
+
+        // ignore . and .. which are zeroes for some reason
+        if (thread_id != 0 && thread_id != main_pid) {
+          struct sched_param param;
+          param.sched_priority = 56;
+          sched_setscheduler(thread_id, SCHED_FIFO, &param);
+        }
+      }
+      closedir(dirp);
+    }
+
     event_loop.Run();
     LOG(INFO) << "Event loop shutting down";