JShorthouse · November 22, 2023 09:33 · May 1, 2022 · May 1, 2022
diff --git a/main.rs b/main.rs
@@ -40,7 +40,7 @@ impl Drop for CpuSample {
             libc::vm_deallocate(
                 libc::mach_task_self(),
                 self.data as libc::vm_address_t,
-                self.size as libc::vm_size_t * std::mem::size_of::<libc::integer_t>(),
+                self.size * std::mem::size_of::<libc::integer_t>(),
             );
         }
     }

diff --git a/Cargo.toml b/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "cpu_usage"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+libc = "0.2.125"
diff --git a/main.rs b/main.rs
@@ -0,0 +1,93 @@
+// references:
+// https://github.com/hdfssk/bubblemon/blob/master/osx/osx-meter.c#L78
+// https://stackoverflow.com/questions/6785069/get-cpu-percent-usage-on-macos
+// https://github.com/apple/darwin-xnu/blob/main/osfmk/kern/host.c#L1125
+
+// licence: MIT
+
+
+use libc;
+
+struct CoreSample {
+    load: i32,
+    idle: i32,
+}
+
+struct CpuSample {
+    num_cores: u32,
+    data: libc::processor_info_array_t,
+    size: usize,
+}
+
+impl CpuSample {
+    fn core(&self, core_num: usize) -> CoreSample {
+        unsafe {
+            let arr = std::slice::from_raw_parts(self.data, self.size);
+
+            return CoreSample {
+                load: arr[libc::CPU_STATE_MAX as usize * core_num + libc::CPU_STATE_USER as usize]
+                    + arr[libc::CPU_STATE_MAX as usize * core_num + libc::CPU_STATE_SYSTEM as usize],
+                idle: arr[libc::CPU_STATE_MAX as usize * core_num + libc::CPU_STATE_IDLE as usize]
+                    + arr[libc::CPU_STATE_MAX as usize * core_num + libc::CPU_STATE_NICE as usize],
+            };
+        }
+    }
+}
+
+impl Drop for CpuSample {
+    fn drop(&mut self) {
+        unsafe {
+            libc::vm_deallocate(
+                libc::mach_task_self(),
+                self.data as libc::vm_address_t,
+                self.size as libc::vm_size_t * std::mem::size_of::<libc::integer_t>(),
+            );
+        }
+    }
+}
+
+fn measure_cpu_sample() -> CpuSample {
+    unsafe {
+        let mut num_cores: libc::natural_t = 0;
+        let mut cpu_info: libc::processor_info_array_t = std::ptr::null_mut();
+        let mut num_cpu_info: libc::mach_msg_type_number_t = 0;
+
+        libc::host_processor_info(
+            libc::mach_host_self(),
+            libc::PROCESSOR_CPU_LOAD_INFO,
+            &mut num_cores,
+            &mut cpu_info,
+            &mut num_cpu_info,
+        );
+
+        return CpuSample{ num_cores, data: cpu_info, size: num_cpu_info as usize };
+    }
+}
+
+fn main() {
+    let mut prev_sample = measure_cpu_sample();
+    let num_cores = prev_sample.num_cores;
+
+    loop {
+        std::thread::sleep(std::time::Duration::from_secs(1));
+
+        let this_sample = measure_cpu_sample();
+
+        for i in 0..num_cores as usize {
+            let core_now = this_sample.core(i);
+            let core_prev = prev_sample.core(i);
+
+            let load = core_now.load - core_prev.load;
+            let idle = core_now.idle - core_prev.idle;
+            let total = load + idle;
+
+            let percent = load as f32 / total as f32 * 100.0;
+
+            println!("Core {}: {:6.1}", i, percent);
+        }
+
+        prev_sample = this_sample;
+
+        println!("");
+    }
+}
diff --git a/output.txt b/output.txt
@@ -0,0 +1,26 @@
+Core 0:    5.0
+Core 1:    5.9
+Core 2:    3.0
+Core 3:    2.0
+Core 4:   72.3
+Core 5:   29.7
+Core 6:   67.7
+Core 7:   46.5
+
+Core 0:    9.0
+Core 1:    9.1
+Core 2:    8.0
+Core 3:    8.8
+Core 4:   79.0
+Core 5:   59.6
+Core 6:   93.0
+Core 7:   72.5
+
+Core 0:    6.9
+Core 1:    5.9
+Core 2:    4.0
+Core 3:    1.0
+Core 4:   98.0
+Core 5:   56.4
+Core 6:  100.0
+Core 7:   46.5