perf: make mem more compact

crates/compact-bytes/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+ahash = "0.8.3"
 append-only-bytes = "0.1.8"
 fxhash = "0.2.1"
 linked-hash-map = "0.5.6"

crates/compact-bytes/fuzz/Cargo.lock

@@ -2,6 +2,18 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "ahash"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2c99f64d1e06488f620f932677e24bc6e2897582980441ae90a671415bd7ec2f"
+dependencies = [
+ "cfg-if",
+ "getrandom",
+ "once_cell",
+ "version_check",
+]
+
 [[package]]
 name = "append-only-bytes"
 version = "0.1.8"
@@ -32,10 +44,17 @@ dependencies = [
  "jobserver",
 ]
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "compact-bytes"
 version = "0.1.0"
 dependencies = [
+ "ahash",
  "append-only-bytes",
  "fxhash",
  "linked-hash-map",
@@ -70,6 +89,17 @@ dependencies = [
  "byteorder",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be4136b2a15dd319360be1c07d9933517ccf0be8f16bf62a3bee4f0d618df427"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "jobserver"
 version = "0.1.26"
@@ -142,3 +172,15 @@ name = "unicode-ident"
 version = "1.0.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "22049a19f4a68748a168c0fc439f9516686aa045927ff767eca0a85101fb6e73"
+
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"

crates/compact-bytes/src/lib.rs

@@ -2,7 +2,11 @@
 
 use append_only_bytes::{AppendOnlyBytes, BytesSlice};
 use fxhash::FxHasher32;
-use std::{hash::Hasher, num::NonZeroU32, ops::Range};
+use std::{
+    hash::Hasher,
+    num::{NonZeroU16, NonZeroU32},
+    ops::Range,
+};
 
 /// it must be a power of 2
 const DEFAULT_CAPACITY: usize = 1 << 16;
@@ -10,34 +14,28 @@ const MAX_TRIED: usize = 4;
 
 /// # Memory Usage
 ///
-/// The memory usage is capacity * 12 bytes.
+/// The memory usage is capacity * 8 bytes.
 /// The default capacity is 65536 (2^16), so the default memory usage is 0.75MB
 ///
 /// You can set the capacity by calling `with_capacity`. The capacity must be a power of 2.
 pub struct CompactBytes {
     bytes: AppendOnlyBytes,
-    map: Box<[Option<NonZeroU32>]>,
-    pos_and_next: Box<[PosLinkList]>,
+    map: Box<[Option<NonZeroU16>]>,
+    pos: Box<[Option<NonZeroU32>]>,
+    next: Box<[Option<NonZeroU16>]>,
     /// next write index fr pos_and_next
     index: usize,
     capacity: usize,
     mask: usize,
 }
 
-#[derive(Debug, Default, Clone, Copy)]
-struct PosLinkList {
-    /// position in the doc + 1
-    value: Option<NonZeroU32>,
-    /// next pos in the list
-    next: Option<NonZeroU32>,
-}
-
 impl CompactBytes {
     pub fn new() -> Self {
         CompactBytes {
             bytes: AppendOnlyBytes::new(),
             map: vec![None; DEFAULT_CAPACITY].into_boxed_slice(),
-            pos_and_next: vec![Default::default(); DEFAULT_CAPACITY].into_boxed_slice(),
+            pos: vec![None; DEFAULT_CAPACITY].into_boxed_slice(),
+            next: vec![None; DEFAULT_CAPACITY].into_boxed_slice(),
             index: 1,
             capacity: DEFAULT_CAPACITY,
             mask: DEFAULT_CAPACITY - 1,
@@ -50,7 +48,8 @@ impl CompactBytes {
         CompactBytes {
             bytes: AppendOnlyBytes::with_capacity(cap),
             map: vec![None; cap].into_boxed_slice(),
-            pos_and_next: vec![Default::default(); cap].into_boxed_slice(),
+            pos: vec![None; cap.min(DEFAULT_CAPACITY)].into_boxed_slice(),
+            next: vec![None; cap.min(DEFAULT_CAPACITY)].into_boxed_slice(),
             index: 1,
             capacity: cap,
             mask: cap - 1,
@@ -132,11 +131,9 @@ impl CompactBytes {
             let key = hash(self.bytes.as_bytes(), i, self.mask);
             // Override the min position in entry with the current position
             let old = self.map[key];
-            self.pos_and_next[self.index] = PosLinkList {
-                value: Some(unsafe { NonZeroU32::new_unchecked(i as u32 + 1) }),
-                next: old,
-            };
-            self.map[key] = Some(NonZeroU32::new(self.index as u32).unwrap());
+            self.pos[self.index] = Some(unsafe { NonZeroU32::new_unchecked(i as u32 + 1) });
+            self.next[self.index] = old;
+            self.map[key] = Some(NonZeroU16::new(self.index as u16).unwrap());
             self.index = (self.index + 1) & self.mask;
             if self.index == 0 {
                 self.index = 1;
@@ -156,15 +153,16 @@ impl CompactBytes {
         let key = hash(bytes, 0, self.mask);
         match self.map[key] {
             Some(pointer) => {
-                let mut node = self.pos_and_next[pointer.get() as usize];
+                let mut w_pos = self.pos[pointer.get() as usize];
+                let mut next = self.next[pointer.get() as usize];
                 let mut max_len = 0;
                 let mut ans_pos = 0;
                 let mut tried = 0;
-                while let Some(pos) = node.value {
+                while let Some(pos) = w_pos {
                     let pos = pos.get() as usize - 1;
-                    node = node
-                        .next
-                        .map(|x| self.pos_and_next[x.get() as usize])
+                    w_pos = next.map(|x| self.pos[x.get() as usize]).unwrap_or_default();
+                    next = next
+                        .map(|x| self.next[x.get() as usize])
                         .unwrap_or_default();
 
                     let mut len = 0;