Performance improvements:

- reduce contention on mutation_lock by having 256 of them
- better lmdb defaults

src/util/async_hash.rs

@@ -1,7 +1,7 @@
 use bytes::Bytes;
 use digest::Digest;
 
-use tokio::sync::mpsc;
+use tokio::sync::{mpsc, oneshot};
 use tokio::task::JoinHandle;
 
 use crate::data::*;
@@ -27,25 +27,28 @@ pub async fn async_blake2sum(data: Bytes) -> Hash {
 // ----
 
 pub struct AsyncHasher<D: Digest> {
-	sendblk: mpsc::UnboundedSender<Bytes>,
+	sendblk: mpsc::UnboundedSender<(Bytes, oneshot::Sender<()>)>,
 	task: JoinHandle<digest::Output<D>>,
 }
 
 impl<D: Digest> AsyncHasher<D> {
 	pub fn new() -> Self {
-		let (sendblk, mut recvblk) = mpsc::unbounded_channel::<Bytes>();
+		let (sendblk, mut recvblk) = mpsc::unbounded_channel::<(Bytes, oneshot::Sender<()>)>();
 		let task = tokio::task::spawn_blocking(move || {
 			let mut digest = D::new();
-			while let Some(blk) = recvblk.blocking_recv() {
+			while let Some((blk, ch)) = recvblk.blocking_recv() {
 				digest.update(&blk[..]);
+				let _ = ch.send(());
 			}
 			digest.finalize()
 		});
 		Self { sendblk, task }
 	}
 
-	pub fn update(&self, b: Bytes) {
-		self.sendblk.send(b).unwrap()
+	pub async fn update(&self, b: Bytes) {
+		let (tx, rx) = oneshot::channel();
+		self.sendblk.send((b, tx)).unwrap();
+		let _ = rx.await;
 	}
 
 	pub async fn finalize(self) -> digest::Output<D> {