Tree hash cache arena (#836)

* Start adding interop genesis state to lcli

* Use more efficient method to generate genesis state

* Remove duplicate int_to_bytes32

* Add lcli command to change state genesis time

* Add option to allow VC to start with unsynced BN

* Set VC to do parallel key loading

* Don't default to dummy eth1 backend

* Add endpoint to dump operation pool

* Add metrics for op pool

* Remove state clone for slot notifier

* Add mem size approximation for tree hash cache

* Avoid cloning tree hash when getting head

* Avoid cloning tree hash when getting head

* Add working arena-based cached tree hash

* Add another benchmark

* Add pre-allocation for caches

* Make cache nullable

* Fix bugs in cache tree hash

* Add validator tree hash optimization

* Optimize hash_concat

* Make hash32_concat return fixed-len array

* Fix failing API tests

* Add new beacon state cache struct

* Add validator-specific cache

* Separate list and values arenas

* Add parallel validator registry hashing

* Remove MultiTreeHashCache

* Remove cached tree hash macro

* Fix failing tree hash test

* Address Michael's comments

* Add CachedTreeHash impl for ef tests

* Fix messy merge conflict

* Rename cache struct, add comments

* Rename cache struct, add comments

* Remove unnecessary mutability

* Wrap iter in result

* Tidy cached tree hash

* Address Michael comments

* Address more comments

* Use ring::Context

eth2/types/examples/clone_state.rs

@@ -0,0 +1,48 @@
+//! These examples only really exist so we can use them for flamegraph. If they get annoying to
+//! maintain, feel free to delete.
+
+use types::{
+    test_utils::generate_deterministic_keypair, BeaconState, Eth1Data, EthSpec, Hash256,
+    MinimalEthSpec, Validator,
+};
+
+type E = MinimalEthSpec;
+
+fn get_state(validator_count: usize) -> BeaconState<E> {
+    let spec = &E::default_spec();
+    let eth1_data = Eth1Data {
+        deposit_root: Hash256::zero(),
+        deposit_count: 0,
+        block_hash: Hash256::zero(),
+    };
+
+    let mut state = BeaconState::new(0, eth1_data, spec);
+
+    for i in 0..validator_count {
+        state.balances.push(i as u64).expect("should add balance");
+        state
+            .validators
+            .push(Validator {
+                pubkey: generate_deterministic_keypair(i).pk.into(),
+                withdrawal_credentials: Hash256::from_low_u64_le(i as u64),
+                effective_balance: i as u64,
+                slashed: i % 2 == 0,
+                activation_eligibility_epoch: i.into(),
+                activation_epoch: i.into(),
+                exit_epoch: i.into(),
+                withdrawable_epoch: i.into(),
+            })
+            .expect("should add validator");
+    }
+
+    state
+}
+
+fn main() {
+    let validator_count = 1_024;
+    let state = get_state(validator_count);
+
+    for _ in 0..100_000 {
+        let _ = state.clone();
+    }
+}

eth2/types/examples/tree_hash_state.rs

@@ -0,0 +1,54 @@
+//! These examples only really exist so we can use them for flamegraph. If they get annoying to
+//! maintain, feel free to delete.
+
+use ssz::{Decode, Encode};
+use types::{
+    test_utils::generate_deterministic_keypair, BeaconState, Eth1Data, EthSpec, Hash256,
+    MinimalEthSpec, Validator,
+};
+
+type E = MinimalEthSpec;
+
+fn get_state(validator_count: usize) -> BeaconState<E> {
+    let spec = &E::default_spec();
+    let eth1_data = Eth1Data {
+        deposit_root: Hash256::zero(),
+        deposit_count: 0,
+        block_hash: Hash256::zero(),
+    };
+
+    let mut state = BeaconState::new(0, eth1_data, spec);
+
+    for i in 0..validator_count {
+        state.balances.push(i as u64).expect("should add balance");
+        state
+            .validators
+            .push(Validator {
+                pubkey: generate_deterministic_keypair(i).pk.into(),
+                withdrawal_credentials: Hash256::from_low_u64_le(i as u64),
+                effective_balance: i as u64,
+                slashed: i % 2 == 0,
+                activation_eligibility_epoch: i.into(),
+                activation_epoch: i.into(),
+                exit_epoch: i.into(),
+                withdrawable_epoch: i.into(),
+            })
+            .expect("should add validator");
+    }
+
+    state
+}
+
+fn main() {
+    let validator_count = 1_024;
+    let mut state = get_state(validator_count);
+    state.update_tree_hash_cache().expect("should update cache");
+
+    actual_thing::<E>(&mut state);
+}
+
+fn actual_thing<T: EthSpec>(state: &mut BeaconState<T>) {
+    for _ in 0..200_024 {
+        let _ = state.update_tree_hash_cache().expect("should update cache");
+    }
+}