Respect configured sampling interval.

samply/src/windows/profiler.rs

@@ -56,11 +56,15 @@ pub fn start_recording(
     let timebase = std::time::SystemTime::now();
     let timebase = ReferenceTimestamp::from_system_time(timebase);
 
-    let interval_8khz = SamplingInterval::from_nanos(122100); // 8192Hz // only with the higher recording rate?
+    const MIN_INTERVAL_NANOS: u64 = 122100; // 8192 kHz
+    let interval_nanos: u64 = recording_props.interval.as_nanos() as u64;
+    let interval_nanos = interval_nanos.clamp(MIN_INTERVAL_NANOS, u64::MAX);
+    let sampling_interval = SamplingInterval::from_nanos(interval_nanos);
+
     let profile = Profile::new(
         &profile_creation_props.profile_name,
         timebase,
-        interval_8khz, // recording_props.interval.into(),
+        sampling_interval,
     );
 
     let arch = profile_creation_props
@@ -70,7 +74,7 @@ pub fn start_recording(
     // Start xperf.
     let mut xperf =
         Xperf::new(arch.to_string()).unwrap_or_else(|e| panic!("Couldn't find xperf: {e:?}"));
-    xperf.start_xperf(&recording_props.output_file);
+    xperf.start_xperf(&recording_props.output_file, sampling_interval);
 
     let included_processes = match recording_mode {
         RecordingMode::All => {

samply/src/windows/xperf.rs

@@ -2,6 +2,8 @@
 
 use std::path::{Path, PathBuf};
 
+use fxprof_processed_profile::SamplingInterval;
+
 pub struct Xperf {
     arch: String,
     xperf_path: PathBuf,
@@ -44,7 +46,7 @@ impl Xperf {
         )
     }
 
-    pub fn start_xperf(&mut self, output_file: &Path) {
+    pub fn start_xperf(&mut self, output_file: &Path, interval: SamplingInterval) {
         if self.is_running() {
             self.stop_xperf();
         }
@@ -62,12 +64,16 @@ impl Xperf {
             None
         };
 
-        let mut xperf = runas::Command::new(&self.xperf_path);
+        const NANOS_PER_TICK: u64 = 100;
+        let interval_ticks = interval.nanos() / NANOS_PER_TICK;
 
-        xperf.arg("-on");
+        let mut xperf = runas::Command::new(&self.xperf_path);
+        xperf.arg("-SetProfInt");
+        xperf.arg(interval_ticks.to_string());
 
         // Virtualised ARM64 Windows crashes out on PROFILE tracing, so this hidden
         // hack argument lets things still continue to run for development of samply.
+        xperf.arg("-on");
         if !self.virtualized_aarch64_hack {
             xperf.arg("PROC_THREAD+LOADER+PROFILE+CSWITCH");
             xperf.arg("-stackwalk");