Implementation of load average calculation and corresponding /proc entry

Moved everything into the kernel side. Add a SchedulerStats trait

Use 'fixed' to represent fixed-point numbers

Make the loadavg calculation lazy

kernel/src/fs/procfs/loadavg.rs

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! This module offers `/proc/loadavg` file support, which tells the user space
+//! about the cpu load average for the last 1, 5, and 15 minutes.
+//!
+//! Reference: <https://www.man7.org/linux/man-pages/man5/proc_loadavg.5.html>
+
+use alloc::format;
+
+use crate::{
+    fs::{
+        procfs::template::{FileOps, ProcFileBuilder},
+        utils::Inode,
+    },
+    prelude::*,
+    process::posix_thread,
+    sched::{self, loadavg::get_loadavg},
+};
+
+/// Represents the inode at `/proc/loadavg`.
+pub struct LoadAvgFileOps;
+
+impl LoadAvgFileOps {
+    pub fn new_inode(parent: Weak<dyn Inode>) -> Arc<dyn Inode> {
+        ProcFileBuilder::new(Self).parent(parent).build().unwrap()
+    }
+}
+
+impl FileOps for LoadAvgFileOps {
+    fn data(&self) -> Result<Vec<u8>> {
+        let avg = get_loadavg();
+        let (nr_queued, nr_running) = sched::nr_queued_and_running();
+
+        let output = format!(
+            "{:.2} {:.2} {:.2} {}/{} {}\n",
+            avg[0],
+            avg[1],
+            avg[2],
+            nr_running,
+            nr_queued,
+            posix_thread::last_tid(),
+        );
+
+        Ok(output.into_bytes())
+    }
+}