From 57cd7aac33252736565a1f785a6c76858e2a9fc7 Mon Sep 17 00:00:00 2001
From: Brad Stein <Brad.Stein@gmail.com>
Date: Fri, 17 Apr 2026 11:54:36 -0300
Subject: [PATCH] lesavka: improve process cpu sampling

---
 client/Cargo.toml             |  2 +-
 common/Cargo.toml             |  2 +-
 common/src/cli.rs             |  2 +-
 common/src/process_metrics.rs | 39 +++++++++++++++++++++++++++++++++++
 server/Cargo.toml             |  2 +-
 5 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/client/Cargo.toml b/client/Cargo.toml
index c791da4..a7987e1 100644
--- a/client/Cargo.toml
+++ b/client/Cargo.toml
@@ -4,7 +4,7 @@ path                    = "src/main.rs"
 
 [package]
 name                    = "lesavka_client"
-version                 = "0.11.2"
+version                 = "0.11.3"
 edition                 = "2024"
 
 [dependencies]
diff --git a/common/Cargo.toml b/common/Cargo.toml
index cbf031c..e690d76 100644
--- a/common/Cargo.toml
+++ b/common/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name                    = "lesavka_common"
-version                 = "0.11.2"
+version                 = "0.11.3"
 edition                 = "2024"
 build                   = "build.rs"
 
diff --git a/common/src/cli.rs b/common/src/cli.rs
index 34aa87e..9d28050 100644
--- a/common/src/cli.rs
+++ b/common/src/cli.rs
@@ -17,6 +17,6 @@ mod tests {
 
     #[test]
     fn banner_includes_version() {
-        assert_eq!(banner("0.11.2"), "lesavka-common CLI (v0.11.2)");
+        assert_eq!(banner("0.11.3"), "lesavka-common CLI (v0.11.3)");
     }
 }
diff --git a/common/src/process_metrics.rs b/common/src/process_metrics.rs
index cfa83ee..96cb642 100644
--- a/common/src/process_metrics.rs
+++ b/common/src/process_metrics.rs
@@ -1,6 +1,7 @@
 #![forbid(unsafe_code)]
 
 use std::time::Instant;
+use std::{process::Command, sync::OnceLock};
 
 /// Sample per-process CPU pressure from Linux procfs.
 ///
@@ -41,10 +42,43 @@ impl ProcessCpuSampler {
 }
 
 fn read_process_runtime_ns() -> Option<u64> {
+    read_process_runtime_from_stat().or_else(read_process_runtime_from_schedstat)
+}
+
+fn read_process_runtime_from_stat() -> Option<u64> {
+    let text = std::fs::read_to_string("/proc/self/stat").ok()?;
+    let close = text.rfind(')')?;
+    let rest = text.get(close + 2..)?;
+    let fields: Vec<&str> = rest.split_whitespace().collect();
+    let utime_ticks = fields.get(11)?.parse::<u64>().ok()?;
+    let stime_ticks = fields.get(12)?.parse::<u64>().ok()?;
+    let total_ticks = utime_ticks.saturating_add(stime_ticks);
+    let ticks_per_second = *clock_ticks_per_second()?;
+    Some(total_ticks.saturating_mul(1_000_000_000) / ticks_per_second.max(1))
+}
+
+fn read_process_runtime_from_schedstat() -> Option<u64> {
     let text = std::fs::read_to_string("/proc/self/schedstat").ok()?;
     text.split_whitespace().next()?.parse::<u64>().ok()
 }
 
+fn clock_ticks_per_second() -> Option<&'static u64> {
+    static CLOCK_TICKS_PER_SECOND: OnceLock<Option<u64>> = OnceLock::new();
+    CLOCK_TICKS_PER_SECOND
+        .get_or_init(|| {
+            let output = Command::new("getconf").arg("CLK_TCK").output().ok()?;
+            if !output.status.success() {
+                return None;
+            }
+            String::from_utf8(output.stdout)
+                .ok()?
+                .trim()
+                .parse::<u64>()
+                .ok()
+        })
+        .as_ref()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -56,6 +90,11 @@ mod tests {
         assert!(read_process_runtime_ns().is_some());
     }
 
+    #[test]
+    fn clock_tick_lookup_reads() {
+        assert!(clock_ticks_per_second().is_some());
+    }
+
     #[test]
     fn sampler_returns_percentage_after_two_samples() {
         let mut sampler = ProcessCpuSampler::new();
diff --git a/server/Cargo.toml b/server/Cargo.toml
index ee9f859..46c7fe6 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -10,7 +10,7 @@ bench                   = false
 
 [package]
 name                    = "lesavka_server"
-version                 = "0.11.2"
+version                 = "0.11.3"
 edition                 = "2024"
 autobins                = false