src: Preallocate a number of stacks on first launch() to actually leverage pool allocator

Author: solb

src/lib.rs

@@ -19,6 +19,8 @@ mod unfurl;
 pub use linger::*;
 
 const QUANTUM_MICROSECS: u64  = 100;
+
+const STACK_N_PREALLOC: usize = 511;
 const STACK_SIZE_BYTES: usize = 2 * 1_024 * 1_024;
 
 #[cfg(test)]

src/stacks.rs

@@ -1,6 +1,7 @@
 use std::marker::PhantomData;
 use std::ops::Deref;
 use std::ops::DerefMut;
+use super::STACK_N_PREALLOC;
 use super::STACK_SIZE_BYTES;
 use timetravel::stable::StableAddr;
 use timetravel::stable::StableMutAddr;
@@ -9,13 +10,25 @@ use reusable::ReusableSync;
 pub fn alloc_stack() -> ReusableSync<'static, Box<[u8]>> {
 	use compile_assert::assert_sync;
 	use reusable::SyncPool;
+	use std::collections::LinkedList;
 	use std::convert::TryInto;
 	use std::sync::Once;
 
 	static mut STACKS: Option<SyncPool<Box<[u8]>>> = None;
 	static INIT: Once = Once::new();
-	INIT.call_once(|| unsafe {
-		STACKS.replace(SyncPool::new(|| Some(vec![0; STACK_SIZE_BYTES].into_boxed_slice())));
+	INIT.call_once(|| {
+		let stacks: fn() -> _ = || Some(vec![0; STACK_SIZE_BYTES].into_boxed_slice());
+		let stacks = SyncPool::new(stacks);
+
+		let prealloc = &stacks;
+		let _: LinkedList<Box<_>> = (0..STACK_N_PREALLOC).map(|_|
+			prealloc.try_into()
+				.expect("libinger: stack allocator lock was poisoned during init")
+		).collect();
+
+		unsafe {
+			STACKS.replace(stacks);
+		}
 	});
 
 	let stacks = unsafe {