From bb741cf6b4780b6726afd7f5db002b43f0effd31 Mon Sep 17 00:00:00 2001
From: ClementTsang <34804052+ClementTsang@users.noreply.github.com>
Date: Sun, 31 Aug 2025 01:20:21 -0400
Subject: [PATCH] reduce some allocations in amd step

---
 Cargo.toml                                  |  2 +-
 src/collection/amd.rs                       | 15 +++++++++------
 src/collection/processes/linux/mod.rs       |  4 +---
 src/collection/processes/unix/user_table.rs |  4 +++-
 4 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 3f2df0a1..4da48754 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -124,7 +124,7 @@ strum = { version = "0.27.2", features = ["derive"], optional = true }
 libc = "0.2.175"
 
 [target.'cfg(target_os = "linux")'.dependencies]
-rustix = { version = "1.0.8", features = ["fs", "param"] }
+rustix = { version = "1.0.8", features = ["fs", "param", "alloc"] }
 
 [target.'cfg(target_os = "macos")'.dependencies]
 core-foundation = "0.10.1"
diff --git a/src/collection/amd.rs b/src/collection/amd.rs
index 18fe5d73..6b813037 100644
--- a/src/collection/amd.rs
+++ b/src/collection/amd.rs
@@ -162,7 +162,7 @@ fn diff_usage(pre: u64, cur: u64, interval: &Duration) -> u64 {
 }
 
 // from amdgpu_top: https://github.com/Umio-Yasuno/amdgpu_top/blob/c961cf6625c4b6d63fda7f03348323048563c584/crates/libamdgpu_top/src/stat/fdinfo/proc_info.rs#L13-L27
-fn get_amdgpu_pid_fds(pid: u32, device_path: Vec<PathBuf>) -> Option<Vec<u32>> {
+fn get_amdgpu_pid_fds(pid: u32, device_path: &[String]) -> Option<Vec<u32>> {
     let Ok(fd_list) = fs::read_dir(format!("/proc/{pid}/fd/")) else {
         return None;
     };
@@ -170,10 +170,13 @@ fn get_amdgpu_pid_fds(pid: u32, device_path: Vec<PathBuf>) -> Option<Vec<u32>> {
     let valid_fds: Vec<u32> = fd_list
         .filter_map(|fd_link| {
             let dir_entry = fd_link.map(|fd_link| fd_link.path()).ok()?;
-            let link = fs::read_link(&dir_entry).ok()?;
+            let link = rustix::fs::readlink(&dir_entry, vec![]).ok()?;
 
             // e.g. "/dev/dri/renderD128" or "/dev/dri/card0"
-            if device_path.iter().any(|path| link.starts_with(path)) {
+            if device_path
+                .iter()
+                .any(|path| link.to_string_lossy().starts_with(path))
+            {
                 dir_entry.file_name()?.to_str()?.parse::<u32>().ok()
             } else {
                 None
@@ -188,7 +191,7 @@ fn get_amdgpu_pid_fds(pid: u32, device_path: Vec<PathBuf>) -> Option<Vec<u32>> {
     }
 }
 
-fn get_amdgpu_drm(device_path: &Path) -> Option<Vec<PathBuf>> {
+fn get_amdgpu_drm(device_path: &Path) -> Option<Vec<String>> {
     let mut drm_devices = Vec::new();
     let drm_root = device_path.join("drm");
 
@@ -212,7 +215,7 @@ fn get_amdgpu_drm(device_path: &Path) -> Option<Vec<PathBuf>> {
             continue;
         }
 
-        drm_devices.push(PathBuf::from(format!("/dev/dri/{drm_name}")));
+        drm_devices.push(format!("/dev/dri/{drm_name}"));
     }
 
     if drm_devices.is_empty() {
@@ -254,7 +257,7 @@ fn get_amd_fdinfo(device_path: &Path) -> Option<HashMap<u32, AmdGpuProc>> {
 
     for pid in pids {
         // collect file descriptors that point to our device renderers
-        let Some(fds) = get_amdgpu_pid_fds(pid, drm_paths.clone()) else {
+        let Some(fds) = get_amdgpu_pid_fds(pid, &drm_paths) else {
             continue;
         };
 
diff --git a/src/collection/processes/linux/mod.rs b/src/collection/processes/linux/mod.rs
index 992722e3..a64952f7 100644
--- a/src/collection/processes/linux/mod.rs
+++ b/src/collection/processes/linux/mod.rs
@@ -137,7 +137,7 @@ fn read_proc(
     thread_parent: Option<Pid>,
 ) -> CollectionResult<(ProcessHarvest, u64)> {
     let Process {
-        pid: _pid,
+        pid: _,
         uid,
         stat,
         io,
@@ -366,8 +366,6 @@ pub(crate) fn linux_process_data(
         prev_non_idle,
     } = prev_proc;
 
-    // TODO: [PROC THREADS] Add threads
-
     let CpuUsage {
         mut cpu_usage,
         cpu_fraction,
diff --git a/src/collection/processes/unix/user_table.rs b/src/collection/processes/unix/user_table.rs
index a9d48378..b2836a51 100644
--- a/src/collection/processes/unix/user_table.rs
+++ b/src/collection/processes/unix/user_table.rs
@@ -8,11 +8,13 @@ pub struct UserTable {
 }
 
 impl UserTable {
+    /// Get the username associated with a UID. On first access of a name, it will
+    /// be cached for future accesses.
     pub fn uid_to_username(&mut self, uid: libc::uid_t) -> CollectionResult<String> {
         if let Some(user) = self.uid_user_mapping.get(&uid) {
             Ok(user.clone())
         } else {
-            // SAFETY: getpwuid returns a null pointer if no passwd entry is found for the uid.
+            // SAFETY: getpwuid returns a null pointer if no passwd entry is found for the uid which we check.
             let passwd = unsafe { libc::getpwuid(uid) };
 
             if passwd.is_null() {