From ef9d8021d69bdad44cbd7deea6220736da58a808 Mon Sep 17 00:00:00 2001
From: Andrew Budge <andrewcbudge@gmail.com>
Date: Wed, 17 Jun 2026 12:35:44 -0600
Subject: [PATCH] perf: avoid sysinfo System::new_all() when only one metric is
 needed
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Found via the criterion suite: parse/10_simple and parse/1000_simple both
cost a flat ~50ms, while the DAG engine builds 10,000 rules in 3ms. A fixed
cost independent of workload size pointed at WorkflowConfig::validate(),
which called sysinfo::System::new_all() — walking all of /proc (every
process, disk, and NIC) — just to read total system memory.

Probe only RAM with System::new() + refresh_memory(). total_memory() still
returns bytes in sysinfo 0.38, so behavior is unchanged. Same fix applied to
executor::available_memory_gb, available_threads (now num_cpus::get()), and
process::detect_total_memory_mb.

parse/10_simple: 50ms -> 39us. All 890 lib tests pass; fmt + clippy clean.
---
 crates/oxo-flow-core/src/config.rs           | 5 ++++-
 crates/oxo-flow-core/src/executor/mod.rs     | 6 ++++--
 crates/oxo-flow-core/src/executor/process.rs | 3 ++-
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/crates/oxo-flow-core/src/config.rs b/crates/oxo-flow-core/src/config.rs
index 3d49926..c70eba9 100644
--- a/crates/oxo-flow-core/src/config.rs
+++ b/crates/oxo-flow-core/src/config.rs
@@ -1267,7 +1267,10 @@ impl WorkflowConfig {
         let system_threads = num_cpus::get() as u32;
         let system_memory_mb = {
             use sysinfo::System;
-            let mut sys = System::new_all();
+            // Only memory is needed here; `System::new_all()` would walk all of
+            // /proc (every process, disk, and network interface) just to read
+            // total RAM, adding ~50ms to every parse/validate/dry-run/run call.
+            let mut sys = System::new();
             sys.refresh_memory();
             sys.total_memory() / 1024 / 1024
         };
diff --git a/crates/oxo-flow-core/src/executor/mod.rs b/crates/oxo-flow-core/src/executor/mod.rs
index 638fcdc..4c76b7a 100644
--- a/crates/oxo-flow-core/src/executor/mod.rs
+++ b/crates/oxo-flow-core/src/executor/mod.rs
@@ -17,13 +17,15 @@ mod tests;
 /// Get available CPU threads for auto-scaling.
 #[must_use]
 pub fn available_threads() -> u32 {
-    System::new_all().cpus().len() as u32
+    num_cpus::get() as u32
 }
 
 /// Get available memory in GB for auto-scaling.
 #[must_use]
 pub fn available_memory_gb() -> u64 {
-    let mut sys = System::new_all();
+    // Only memory is needed; `System::new_all()` would also walk every process,
+    // disk, and network interface in /proc for no reason.
+    let mut sys = System::new();
     sys.refresh_memory();
     sys.available_memory() / (1024 * 1024 * 1024) // Convert bytes to GB
 }
diff --git a/crates/oxo-flow-core/src/executor/process.rs b/crates/oxo-flow-core/src/executor/process.rs
index 2d15798..3b1eb5e 100644
--- a/crates/oxo-flow-core/src/executor/process.rs
+++ b/crates/oxo-flow-core/src/executor/process.rs
@@ -300,7 +300,8 @@ fn detect_total_memory_mb() -> u64 {
     // Primary: sysinfo crate (cross-platform)
     if let Ok(mb) = std::panic::catch_unwind(|| {
         use sysinfo::System;
-        let mut sys = System::new_all();
+        // Only memory is needed; avoid `System::new_all()` scanning all of /proc.
+        let mut sys = System::new();
         sys.refresh_memory();
         sys.total_memory() / 1024 / 1024
     }) && mb > 0