fix(perf): run with --scope to allow perf to trace the benchmark process

Author: not-matthias

src/run/runner/wall_time/executor.rs

@@ -34,7 +34,11 @@ impl WallTimeExecutor {
                     .into_iter()
                     .map(|(k, v)| (k.into(), v)),
             )
-            .map(|(env, value)| format!("{env}={value}"))
+            .map(|(env, value)| {
+                // Properly quote the value to handle special characters
+                let escaped_value = value.replace("\\", "\\\\").replace("\"", "\\\"");
+                format!("export {env}=\"{escaped_value}\"")
+            })
             .collect::<Vec<_>>()
             .join("\n");
 
@@ -49,8 +53,15 @@ impl WallTimeExecutor {
 
         let uid = nix::unistd::Uid::current().as_raw();
         let gid = nix::unistd::Gid::current().as_raw();
+
+        // Remarks:
+        // - We're using --scope so that perf is able to capture the events of the benchmark process.
+        // - We can't user `--user` here because we need to run in `codspeed.slice`, otherwise we'd run in
+        //   user.slice` (which is isolated). We can use `--gid` and `--uid` to run the command as the current user.
+        // - We must use `bash` here instead of `sh` since `source` isn't available when symlinked to `dash`.
+        // - We have to pass the environment variables because `--scope` only inherits the system and not the user environment variables.
         let cmd = format!(
-            "systemd-run {quiet_flag} --pipe --collect --wait --slice=codspeed.slice --same-dir --uid={uid} --gid={gid} --property=EnvironmentFile={} -- sh -c '{}'",
+            "systemd-run {quiet_flag} --scope --slice=codspeed.slice --same-dir --uid={uid} --gid={gid} -- bash -c 'source {} && {}'",
             env_file.path().display(),
             bench_cmd.replace("'", "\"")
         );

src/run/runner/wall_time/perf/helpers.rs

@@ -1,7 +1,6 @@
-use std::collections::HashMap;
-
-use anyhow::{anyhow, bail};
+use crate::prelude::*;
 use linux_perf_data::{PerfFileReader, PerfFileRecord, linux_perf_event_reader::EventRecord};
+use std::collections::HashMap;
 
 /// Tries to find the pid of the sampled process within a perf.data file.
 pub fn find_pid<P: AsRef<std::path::Path>>(perf_file: P) -> anyhow::Result<i32> {
@@ -48,6 +47,7 @@ pub fn find_pid<P: AsRef<std::path::Path>>(perf_file: P) -> anyhow::Result<i32>
             }
         }
     }
+    debug!("Pid frequency: {pid_freq:?}");
 
     // Choose the pid with the highest frequency. However, we can only use a pid if more than N% of the
     // events are from that pid.

src/run/runner/wall_time/perf/mod.rs

@@ -251,7 +251,10 @@ impl PerfRunner {
         let perf_map_pids = futures::future::try_join_all(copy_tasks)
             .await?
             .into_iter()
-            .filter_map(Result::ok)
+            .filter_map(|result| {
+                debug!("Copy task result: {result:?}");
+                result.ok()
+            })
             .collect::<HashSet<_>>();
         harvest_perf_maps_for_pids(profile_folder, &perf_map_pids).await?;