fix(config): enable allocator reclaim by default (#6566)

Co-authored-by: heihutu <heihutu@gmail.com>

rustfs/src/allocator_reclaim.rs

@@ -18,8 +18,8 @@
 //! GET, scanner, and heal workloads, mimalloc can retain freed pages in process
 //! heaps for later reuse instead of immediately returning them to the OS. That
 //! behavior is usually good for latency, but it can make process RSS look high
-//! after a workload has gone idle. This module provides an opt-in background
-//! loop that waits for a configurable idle window and then asks the allocator to
+//! after a workload has gone idle. This module provides a configurable
+//! background loop that waits for an idle window and then asks the allocator to
 //! collect retained memory.
 //!
 //! The loop is intentionally conservative:
@@ -41,7 +41,7 @@ use metrics::{counter, gauge, histogram};
 use serde::Serialize;
 use std::time::Duration;
 use tokio_util::sync::CancellationToken;
-use tracing::{debug, warn};
+use tracing::{debug, info, warn};
 
 const ALLOCATOR_RECLAIM_SERVICE_NAME: &str = "allocator_reclaim";
 
@@ -238,8 +238,9 @@ fn reclaimable_work_snapshot() -> ReclaimableWorkSnapshot {
 
 /// Read the startup enablement switch.
 ///
-/// The code default is disabled. Local developer scripts may choose to export
-/// the variable as enabled for their own launch profile.
+/// The code default is enabled so direct binary, container, Helm, and local
+/// script launches share the same reclaim contract. Operators can still set
+/// `RUSTFS_ALLOCATOR_RECLAIM_ENABLED=false` for latency-sensitive deployments.
 fn configured_allocator_reclaim_enabled() -> bool {
     rustfs_utils::get_env_bool(
         rustfs_config::ENV_ALLOCATOR_RECLAIM_ENABLED,
@@ -421,15 +422,27 @@ pub fn init_allocator_reclaim(ctx: CancellationToken) {
     gauge!("rustfs_memory_allocator_reclaim_enabled").set(if enabled { 1.0 } else { 0.0 });
     counter!("rustfs_memory_allocator_backend_info", "backend" => backend.to_string()).increment(1);
 
-    if !enabled {
-        debug!("allocator reclaim loop disabled");
-        return;
-    }
-
     let configured_force = configured_allocator_reclaim_force();
     let force = effective_allocator_reclaim_force(backend, configured_force);
     let idle_intervals = configured_allocator_reclaim_idle_intervals();
     let interval = Duration::from_secs(configured_allocator_reclaim_interval_secs());
+    info!(
+        event = "allocator_reclaim_configured",
+        component = "runtime",
+        subsystem = "memory",
+        state = if enabled { "enabled" } else { "disabled" },
+        backend,
+        configured_force,
+        effective_force = force,
+        idle_intervals,
+        interval_secs = interval.as_secs(),
+        "allocator reclaim configured"
+    );
+
+    if !enabled {
+        debug!("allocator reclaim loop disabled");
+        return;
+    }
 
     tokio::spawn(async move {
         let mut ticker = tokio::time::interval(interval);

rustfs/src/config/cli.rs

@@ -302,6 +302,11 @@ pub struct TlsInspectOpts {
 
 /// Server subcommand options
 #[derive(Args, Clone)]
+#[command(after_help = "Allocator reclaim environment:
+  RUSTFS_ALLOCATOR_RECLAIM_ENABLED=true|false  Enable allocator page reclaim after idle samples (default: true)
+  RUSTFS_ALLOCATOR_RECLAIM_INTERVAL_SECS=30    Sampling interval in seconds
+  RUSTFS_ALLOCATOR_RECLAIM_FORCE=true|false    Request forceful collection when supported
+  RUSTFS_ALLOCATOR_RECLAIM_IDLE_INTERVALS=3    Consecutive idle samples required before reclaim")]
 pub struct ServerOpts {
     /// DIR points to a directory on a filesystem.
     #[arg(
@@ -612,4 +617,23 @@ mod tests {
         assert_eq!(help.kind(), ErrorKind::DisplayHelp);
         assert!(help.to_string().contains("Unix only"));
     }
+
+    #[test]
+    fn server_help_lists_allocator_reclaim_environment() {
+        let result = Cli::try_parse_from(["rustfs", "server", "--help"]);
+        let Err(help) = result else {
+            panic!("help exits without parsing server options");
+        };
+
+        assert_eq!(help.kind(), ErrorKind::DisplayHelp);
+        let help = help.to_string();
+        for env in [
+            "RUSTFS_ALLOCATOR_RECLAIM_ENABLED",
+            "RUSTFS_ALLOCATOR_RECLAIM_INTERVAL_SECS",
+            "RUSTFS_ALLOCATOR_RECLAIM_FORCE",
+            "RUSTFS_ALLOCATOR_RECLAIM_IDLE_INTERVALS",
+        ] {
+            assert!(help.contains(env), "server help should mention {env}");
+        }
+    }
 }