Add an additional NUM_CPUS atomic to store the actual size. CPU

utilization is updated in a lock-free array of atomics. Another
lock removed (and another unmeasurably small gain)

src/rust/Cargo.lock

@@ -1359,6 +1359,7 @@ dependencies = [
  "lqos_config",
  "lqos_utils",
  "nix",
+ "once_cell",
  "parking_lot",
  "rocket",
  "rocket_async_compression",

src/rust/lqos_node_manager/Cargo.toml

@@ -19,6 +19,7 @@ anyhow = "1"
 sysinfo = "0"
 default-net = "0"
 nix = "0"
+once_cell = "1"
 
 # Support JemAlloc on supported platforms
 [target.'cfg(any(target_arch = "x86", target_arch = "x86_64"))'.dependencies]

src/rust/lqos_node_manager/src/tracker/cache/cpu_ram.rs

@@ -1,12 +1,24 @@
-use std::sync::atomic::AtomicU64;
+use std::sync::atomic::{AtomicU64, AtomicU32, AtomicUsize};
+use once_cell::sync::Lazy;
 
-use lazy_static::*;
-use parking_lot::RwLock;
+const MAX_CPUS_COUNTED: usize = 128;
 
-lazy_static! {
-    /// Global storage of current CPU usage
-    pub static ref CPU_USAGE : RwLock<Vec<f32>> = RwLock::new(Vec::with_capacity(128));
-}
+/// Stores overall CPU usage
+pub static CPU_USAGE: Lazy<[AtomicU32; MAX_CPUS_COUNTED]> = Lazy::new(build_empty_cpu_list);
 
+/// Total number of CPUs detected
+pub static NUM_CPUS: AtomicUsize = AtomicUsize::new(0);
+
+/// Total RAM used (bytes)
 pub static RAM_USED: AtomicU64 = AtomicU64::new(0);
-pub static TOTAL_RAM: AtomicU64 = AtomicU64::new(0);
+
+/// Total RAM installed (bytes)
+pub static TOTAL_RAM: AtomicU64 = AtomicU64::new(0);
+
+fn build_empty_cpu_list() -> [AtomicU32; MAX_CPUS_COUNTED] {
+    let mut temp = Vec::with_capacity(MAX_CPUS_COUNTED);
+    for _ in 0..MAX_CPUS_COUNTED {
+        temp.push(AtomicU32::new(0));
+    }
+    temp.try_into().expect("This should never happen, sizes are constant.")
+}

src/rust/lqos_node_manager/src/tracker/cache_manager.rs

@@ -53,12 +53,15 @@ pub async fn update_tracking() {
 
             sys.refresh_cpu();
             sys.refresh_memory();
-            let cpu_usage = sys
+
+            sys
               .cpus()
               .iter()
-              .map(|cpu| cpu.cpu_usage())
-              .collect::<Vec<f32>>();
-            *CPU_USAGE.write() = cpu_usage;
+              .enumerate()
+              .map(|(i, cpu)| (i, cpu.cpu_usage() as u32)) // Always rounds down
+              .for_each(|(i, cpu)| CPU_USAGE[i].store(cpu, std::sync::atomic::Ordering::Relaxed));
+
+            NUM_CPUS.store(sys.cpus().len(), std::sync::atomic::Ordering::Relaxed);
             RAM_USED.store(sys.used_memory(), std::sync::atomic::Ordering::Relaxed);
             TOTAL_RAM.store(sys.total_memory(), std::sync::atomic::Ordering::Relaxed);
             let error = get_data_from_server().await; // Ignoring errors to keep running

src/rust/lqos_node_manager/src/tracker/mod.rs

@@ -2,7 +2,7 @@ mod cache;
 mod cache_manager;
 use self::cache::{
   CPU_USAGE, CURRENT_THROUGHPUT, HOST_COUNTS, RAM_USED, TOTAL_RAM, RTT_HISTOGRAM,
-  THROUGHPUT_BUFFER, TOP_10_DOWNLOADERS, WORST_10_RTT,
+  THROUGHPUT_BUFFER, TOP_10_DOWNLOADERS, WORST_10_RTT, NUM_CPUS,
 };
 use crate::{auth_guard::AuthGuard, tracker::cache::ThroughputPerSecond};
 pub use cache::{SHAPED_DEVICES, UNKNOWN_DEVICES};
@@ -70,10 +70,14 @@ pub fn throughput_ring(_auth: AuthGuard) -> Json<Vec<ThroughputPerSecond>> {
 }
 
 #[get("/api/cpu")]
-pub fn cpu_usage(_auth: AuthGuard) -> Json<Vec<f32>> {
-  let cpu_usage = CPU_USAGE.read().clone();
+pub fn cpu_usage(_auth: AuthGuard) -> Json<Vec<u32>> {
+  let usage: Vec<u32> = CPU_USAGE
+    .iter()
+    .take(NUM_CPUS.load(std::sync::atomic::Ordering::Relaxed))
+    .map(|cpu| cpu.load(std::sync::atomic::Ordering::Relaxed))
+    .collect();
 
-  Json(cpu_usage)
+  Json(usage)
 }
 
 #[get("/api/ram")]