Use SmallVec for TreeHash packed encoding (#3581)

## Issue Addressed NA ## Proposed Changes I've noticed that our block hashing times increase significantly after the merge. I did some flamegraph-ing and noticed that we're allocating a `Vec` for each byte of each execution payload transaction. This seems like unnecessary work and a bit of a fragmentation risk. This PR switches to `SmallVec<[u8; 32]>` for the packed encoding of `TreeHash`. I believe this is a nice simple optimisation with no downside. ### Benchmarking These numbers were computed using #3580 on my desktop (i7 hex-core). You can see a bit of noise in the numbers, that's probably just my computer doing other things. Generally I found this change takes the time from 10-11ms to 8-9ms. I can also see all the allocations disappear from flamegraph. This is the block being benchmarked: https://beaconcha.in/slot/4704236 #### Before ``` [2022-09-15T21:44:19Z INFO lcli::block_root] Run 980: 10.553003ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 981: 10.563737ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 982: 10.646352ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 983: 10.628532ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 984: 10.552112ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 985: 10.587778ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 986: 10.640526ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 987: 10.587243ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 988: 10.554748ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 989: 10.551111ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 990: 11.559031ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 991: 11.944827ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 992: 10.554308ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 993: 11.043397ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 994: 11.043315ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 995: 11.207711ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 996: 11.056246ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 997: 11.049706ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 998: 11.432449ms [2022-09-15T21:44:19Z INFO lcli::block_root] Run 999: 11.149617ms ``` #### After ``` [2022-09-15T21:41:49Z INFO lcli::block_root] Run 980: 14.011653ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 981: 8.925314ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 982: 8.849563ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 983: 8.893689ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 984: 8.902964ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 985: 8.942067ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 986: 8.907088ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 987: 9.346101ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 988: 8.96142ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 989: 9.366437ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 990: 9.809334ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 991: 9.541561ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 992: 11.143518ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 993: 10.821181ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 994: 9.855973ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 995: 10.941006ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 996: 9.596155ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 997: 9.121739ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 998: 9.090019ms [2022-09-15T21:41:49Z INFO lcli::block_root] Run 999: 9.071885ms ``` ## Additional Info Please provide any additional information. For example, future considerations or information useful for reviewers.
2024-12-22 11:41:28 +00:00 · 2022-09-16 08:54:06 +00:00 · 2022-09-16 08:54:06 +00:00 · b0b606dabe
commit b0b606dabe
parent bde3c168e2
15 changed files with 44 additions and 41 deletions
--- a/consensus/ssz_types/src/bitfield.rs
+++ b/consensus/ssz_types/src/bitfield.rs
@ -620,7 +620,7 @@ impl<N: Unsigned + Clone> tree_hash::TreeHash for Bitfield<Variable<N>> {
        tree_hash::TreeHashType::List
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
        unreachable!("List should never be packed.")
    }

@ -641,7 +641,7 @@ impl<N: Unsigned + Clone> tree_hash::TreeHash for Bitfield<Fixed<N>> {
        tree_hash::TreeHashType::Vector
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
        unreachable!("Vector should never be packed.")
    }

--- a/consensus/ssz_types/src/fixed_vector.rs
+++ b/consensus/ssz_types/src/fixed_vector.rs
@ -167,7 +167,7 @@ where
        tree_hash::TreeHashType::Vector
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
        unreachable!("Vector should never be packed.")
    }

--- a/consensus/ssz_types/src/variable_list.rs
+++ b/consensus/ssz_types/src/variable_list.rs
@ -184,7 +184,7 @@ where
        tree_hash::TreeHashType::List
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
        unreachable!("List should never be packed.")
    }

--- a/consensus/tree_hash/src/impls.rs
+++ b/consensus/tree_hash/src/impls.rs
@ -14,8 +14,8 @@ macro_rules! impl_for_bitsize {
                TreeHashType::Basic
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-                self.to_le_bytes().to_vec()
+            fn tree_hash_packed_encoding(&self) -> PackedEncoding {
+                PackedEncoding::from_slice(&self.to_le_bytes())
            }

            fn tree_hash_packing_factor() -> usize {
@ -41,7 +41,7 @@ impl TreeHash for bool {
        TreeHashType::Basic
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
        (*self as u8).tree_hash_packed_encoding()
    }

@ -62,7 +62,7 @@ macro_rules! impl_for_lt_32byte_u8_array {
                TreeHashType::Vector
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> PackedEncoding {
                unreachable!("bytesN should never be packed.")
            }

@ -87,10 +87,10 @@ impl TreeHash for U128 {
        TreeHashType::Basic
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-        let mut result = vec![0; 16];
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
+        let mut result = [0; 16];
        self.to_little_endian(&mut result);
-        result
+        PackedEncoding::from_slice(&result)
    }

    fn tree_hash_packing_factor() -> usize {
@ -109,10 +109,10 @@ impl TreeHash for U256 {
        TreeHashType::Basic
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-        let mut result = vec![0; 32];
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
+        let mut result = [0; 32];
        self.to_little_endian(&mut result);
-        result
+        PackedEncoding::from_slice(&result)
    }

    fn tree_hash_packing_factor() -> usize {
@ -131,10 +131,10 @@ impl TreeHash for H160 {
        TreeHashType::Vector
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-        let mut result = vec![0; 32];
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
+        let mut result = [0; 32];
        result[0..20].copy_from_slice(self.as_bytes());
-        result
+        PackedEncoding::from_slice(&result)
    }

    fn tree_hash_packing_factor() -> usize {
@ -153,8 +153,8 @@ impl TreeHash for H256 {
        TreeHashType::Vector
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-        self.as_bytes().to_vec()
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
+        PackedEncoding::from_slice(self.as_bytes())
    }

    fn tree_hash_packing_factor() -> usize {
--- a/consensus/tree_hash/src/lib.rs
+++ b/consensus/tree_hash/src/lib.rs
@ -8,13 +8,16 @@ pub use merkleize_padded::merkleize_padded;
 pub use merkleize_standard::merkleize_standard;

 use eth2_hashing::{hash_fixed, ZERO_HASHES, ZERO_HASHES_MAX_INDEX};
+use smallvec::SmallVec;

 pub const BYTES_PER_CHUNK: usize = 32;
 pub const HASHSIZE: usize = 32;
 pub const MERKLE_HASH_CHUNK: usize = 2 * BYTES_PER_CHUNK;
 pub const MAX_UNION_SELECTOR: u8 = 127;
+pub const SMALLVEC_SIZE: usize = 32;

 pub type Hash256 = ethereum_types::H256;
+pub type PackedEncoding = SmallVec<[u8; SMALLVEC_SIZE]>;

 /// Convenience method for `MerkleHasher` which also provides some fast-paths for small trees.
 ///
@ -109,7 +112,7 @@ pub enum TreeHashType {
 pub trait TreeHash {
    fn tree_hash_type() -> TreeHashType;

-    fn tree_hash_packed_encoding(&self) -> Vec<u8>;
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding;

    fn tree_hash_packing_factor() -> usize;

@ -125,7 +128,7 @@ where
        T::tree_hash_type()
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
        T::tree_hash_packed_encoding(*self)
    }

@ -146,7 +149,7 @@ macro_rules! tree_hash_ssz_encoding_as_vector {
                tree_hash::TreeHashType::Vector
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> PackedEncoding {
                unreachable!("Vector should never be packed.")
            }

@ -169,7 +172,7 @@ macro_rules! tree_hash_ssz_encoding_as_list {
                tree_hash::TreeHashType::List
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> PackedEncoding {
                unreachable!("List should never be packed.")
            }

--- a/consensus/tree_hash/tests/tests.rs
+++ b/consensus/tree_hash/tests/tests.rs
@ -1,5 +1,5 @@
 use ssz_derive::Encode;
-use tree_hash::{Hash256, MerkleHasher, TreeHash, BYTES_PER_CHUNK};
+use tree_hash::{Hash256, MerkleHasher, PackedEncoding, TreeHash, BYTES_PER_CHUNK};
 use tree_hash_derive::TreeHash;

 #[derive(Encode)]
@ -18,7 +18,7 @@ impl tree_hash::TreeHash for HashVec {
        tree_hash::TreeHashType::List
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
        unreachable!("List should never be packed.")
    }

--- a/consensus/tree_hash_derive/src/lib.rs
+++ b/consensus/tree_hash_derive/src/lib.rs
@ -150,7 +150,7 @@ fn tree_hash_derive_struct(item: &DeriveInput, struct_data: &DataStruct) -> Toke
                tree_hash::TreeHashType::Container
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
                unreachable!("Struct should never be packed.")
            }

@ -231,7 +231,7 @@ fn tree_hash_derive_enum_transparent(
                tree_hash::TreeHashType::Container
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
                unreachable!("Enum should never be packed")
            }

@ -288,7 +288,7 @@ fn tree_hash_derive_enum_union(derive_input: &DeriveInput, enum_data: &DataEnum)
                tree_hash::TreeHashType::Container
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
                unreachable!("Enum should never be packed")
            }

--- a/consensus/types/src/execution_block_hash.rs
+++ b/consensus/types/src/execution_block_hash.rs
@ -67,7 +67,7 @@ impl tree_hash::TreeHash for ExecutionBlockHash {
        Hash256::tree_hash_type()
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
        self.0.tree_hash_packed_encoding()
    }

--- a/consensus/types/src/graffiti.rs
+++ b/consensus/types/src/graffiti.rs
@ -7,7 +7,7 @@ use serde::{de::Error, Deserialize, Deserializer, Serialize, Serializer};
 use ssz::{Decode, DecodeError, Encode};
 use std::fmt;
 use std::str::FromStr;
-use tree_hash::TreeHash;
+use tree_hash::{PackedEncoding, TreeHash};

 pub const GRAFFITI_BYTES_LEN: usize = 32;

@ -159,7 +159,7 @@ impl TreeHash for Graffiti {
        <[u8; GRAFFITI_BYTES_LEN]>::tree_hash_type()
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
        self.0.tree_hash_packed_encoding()
    }

--- a/consensus/types/src/participation_flags.rs
+++ b/consensus/types/src/participation_flags.rs
@ -3,7 +3,7 @@ use safe_arith::{ArithError, SafeArith};
 use serde_derive::{Deserialize, Serialize};
 use ssz::{Decode, DecodeError, Encode};
 use test_random_derive::TestRandom;
-use tree_hash::{TreeHash, TreeHashType};
+use tree_hash::{PackedEncoding, TreeHash, TreeHashType};

 #[derive(Debug, Default, Clone, Copy, PartialEq, Deserialize, Serialize, TestRandom)]
 #[serde(transparent)]
@ -78,7 +78,7 @@ impl TreeHash for ParticipationFlags {
        u8::tree_hash_type()
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
        self.bits.tree_hash_packed_encoding()
    }

--- a/consensus/types/src/payload.rs
+++ b/consensus/types/src/payload.rs
@ -7,7 +7,7 @@ use std::convert::TryFrom;
 use std::fmt::Debug;
 use std::hash::Hash;
 use test_random_derive::TestRandom;
-use tree_hash::TreeHash;
+use tree_hash::{PackedEncoding, TreeHash};

 #[derive(Debug)]
 pub enum BlockType {
@ -175,7 +175,7 @@ impl<T: EthSpec> TreeHash for BlindedPayload<T> {
        <ExecutionPayloadHeader<T>>::tree_hash_type()
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> PackedEncoding {
        self.execution_payload_header.tree_hash_packed_encoding()
    }

@ -244,7 +244,7 @@ impl<T: EthSpec> TreeHash for FullPayload<T> {
        <ExecutionPayload<T>>::tree_hash_type()
    }

-    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+    fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
        self.execution_payload.tree_hash_packed_encoding()
    }

--- a/consensus/types/src/slot_epoch.rs
+++ b/consensus/types/src/slot_epoch.rs
@ -16,7 +16,7 @@ use crate::{ChainSpec, SignedRoot};
 use rand::RngCore;
 use safe_arith::{ArithError, SafeArith};
 use serde_derive::{Deserialize, Serialize};
-use ssz::{ssz_encode, Decode, DecodeError, Encode};
+use ssz::{Decode, DecodeError, Encode};
 use std::fmt;
 use std::hash::Hash;
 use std::iter::Iterator;
--- a/consensus/types/src/slot_epoch_macros.rs
+++ b/consensus/types/src/slot_epoch_macros.rs
@ -290,8 +290,8 @@ macro_rules! impl_ssz {
                tree_hash::TreeHashType::Basic
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-                ssz_encode(self)
+            fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
+                self.0.tree_hash_packed_encoding()
            }

            fn tree_hash_packing_factor() -> usize {
--- a/crypto/bls/src/macros.rs
+++ b/crypto/bls/src/macros.rs
@ -7,7 +7,7 @@ macro_rules! impl_tree_hash {
            tree_hash::TreeHashType::Vector
        }

-        fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+        fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
            unreachable!("Vector should never be packed.")
        }

--- a/testing/ef_tests/src/cases/common.rs
+++ b/testing/ef_tests/src/cases/common.rs
@ -43,7 +43,7 @@ macro_rules! uint_wrapper {
                <$wrapped_type>::tree_hash_type()
            }

-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+            fn tree_hash_packed_encoding(&self) -> tree_hash::PackedEncoding {
                self.x.tree_hash_packed_encoding()
            }