Refactor Bytes to use an internal vtable

Bytes is a useful tool for managing multiple slices into the same region of memory, and the other things it used to have been removed to reduce complexity. The exact strategy for managing the multiple references is no longer hard-coded, but instead backing by a customizable vtable. - Removed ability to mutate the underlying memory from the `Bytes` type. - Removed the "inline" (SBO) mechanism in `Bytes`. The reduces a large amount of complexity, and improves performance when accessing the slice of bytes, since a branch is no longer needed to check if the data is inline. - Removed `Bytes` knowledge of `BytesMut` (`BytesMut` may grow that knowledge back at a future point.)
tokio-rs · Oct 16, 2019 · 493b37a · 493b37a
1 parent ebe9602
commit 493b37a
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Showing 17 changed files with 2,175 additions and 2,829 deletions.
diff --git a/Cargo.toml b/Cargo.toml
@@ -28,4 +28,5 @@ serde = { version = "1.0", optional = true }
 either = { version = "1.5", default-features = false, optional = true }
 
 [dev-dependencies]
+loom = "0.2.10"
 serde_test = "1.0"
diff --git a/benches/bytes.rs b/benches/bytes.rs
@@ -4,47 +4,11 @@
 extern crate test;
 
 use test::Bencher;
-use bytes::{Bytes, BytesMut, BufMut};
-
-#[bench]
-fn alloc_small(b: &mut Bencher) {
-    b.iter(|| {
-        for _ in 0..1024 {
-            test::black_box(BytesMut::with_capacity(12));
-        }
-    })
-}
-
-#[bench]
-fn alloc_mid(b: &mut Bencher) {
-    b.iter(|| {
-        test::black_box(BytesMut::with_capacity(128));
-    })
-}
-
-#[bench]
-fn alloc_big(b: &mut Bencher) {
-    b.iter(|| {
-        test::black_box(BytesMut::with_capacity(4096));
-    })
-}
-
-#[bench]
-fn split_off_and_drop(b: &mut Bencher) {
-    b.iter(|| {
-        for _ in 0..1024 {
-            let v = vec![10; 200];
-            let mut b = Bytes::from(v);
-            test::black_box(b.split_off(100));
-            test::black_box(b);
-        }
-    })
-}
+use bytes::Bytes;
 
 #[bench]
 fn deref_unique(b: &mut Bencher) {
-    let mut buf = BytesMut::with_capacity(4096);
-    buf.put(&[0u8; 1024][..]);
+    let buf = Bytes::from(vec![0; 1024]);
 
     b.iter(|| {
         for _ in 0..1024 {
@@ -53,30 +17,10 @@ fn deref_unique(b: &mut Bencher) {
     })
 }
 
-#[bench]
-fn deref_unique_unroll(b: &mut Bencher) {
-    let mut buf = BytesMut::with_capacity(4096);
-    buf.put(&[0u8; 1024][..]);
-
-    b.iter(|| {
-        for _ in 0..128 {
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-            test::black_box(&buf[..]);
-        }
-    })
-}
-
 #[bench]
 fn deref_shared(b: &mut Bencher) {
-    let mut buf = BytesMut::with_capacity(4096);
-    buf.put(&[0u8; 1024][..]);
-    let _b2 = buf.split_off(1024);
+    let buf = Bytes::from(vec![0; 1024]);
+    let _b2 = buf.clone();
 
     b.iter(|| {
         for _ in 0..1024 {
@@ -86,9 +30,8 @@ fn deref_shared(b: &mut Bencher) {
 }
 
 #[bench]
-fn deref_inline(b: &mut Bencher) {
-    let mut buf = BytesMut::with_capacity(8);
-    buf.put(&[0u8; 8][..]);
+fn deref_static(b: &mut Bencher) {
+    let buf = Bytes::from_static(b"hello world");
 
     b.iter(|| {
         for _ in 0..1024 {
@@ -97,33 +40,6 @@ fn deref_inline(b: &mut Bencher) {
     })
 }
 
-#[bench]
-fn deref_two(b: &mut Bencher) {
-    let mut buf1 = BytesMut::with_capacity(8);
-    buf1.put(&[0u8; 8][..]);
-
-    let mut buf2 = BytesMut::with_capacity(4096);
-    buf2.put(&[0u8; 1024][..]);
-
-    b.iter(|| {
-        for _ in 0..512 {
-            test::black_box(&buf1[..]);
-            test::black_box(&buf2[..]);
-        }
-    })
-}
-
-#[bench]
-fn clone_inline(b: &mut Bencher) {
-    let bytes = Bytes::from_static(b"hello world");
-
-    b.iter(|| {
-        for _ in 0..1024 {
-            test::black_box(&bytes.clone());
-        }
-    })
-}
-
 #[bench]
 fn clone_static(b: &mut Bencher) {
     let bytes = Bytes::from_static("hello world 1234567890 and have a good byte 0987654321".as_bytes());
@@ -136,8 +52,8 @@ fn clone_static(b: &mut Bencher) {
 }
 
 #[bench]
-fn clone_arc(b: &mut Bencher) {
-    let bytes = Bytes::from("hello world 1234567890 and have a good byte 0987654321".as_bytes());
+fn clone_shared(b: &mut Bencher) {
+    let bytes = Bytes::from(b"hello world 1234567890 and have a good byte 0987654321".to_vec());
 
     b.iter(|| {
         for _ in 0..1024 {
@@ -147,42 +63,14 @@ fn clone_arc(b: &mut Bencher) {
 }
 
 #[bench]
-fn alloc_write_split_to_mid(b: &mut Bencher) {
-    b.iter(|| {
-        let mut buf = BytesMut::with_capacity(128);
-        buf.put_slice(&[0u8; 64]);
-        test::black_box(buf.split_to(64));
-    })
-}
-
-#[bench]
-fn drain_write_drain(b: &mut Bencher) {
-    let data = [0u8; 128];
+fn clone_arc_vec(b: &mut Bencher) {
+    use std::sync::Arc;
+    let bytes = Arc::new(b"hello world 1234567890 and have a good byte 0987654321".to_vec());
 
     b.iter(|| {
-        let mut buf = BytesMut::with_capacity(1024);
-        let mut parts = Vec::with_capacity(8);
-
-        for _ in 0..8 {
-            buf.put(&data[..]);
-            parts.push(buf.split_to(128));
+        for _ in 0..1024 {
+            test::black_box(&bytes.clone());
         }
-
-        test::black_box(parts);
-    })
-}
-
-#[bench]
-fn fmt_write(b: &mut Bencher) {
-    use std::fmt::Write;
-    let mut buf = BytesMut::with_capacity(128);
-    let s = "foo bar baz quux lorem ipsum dolor et";
-
-    b.bytes = s.len() as u64;
-    b.iter(|| {
-        let _ = write!(buf, "{}", s);
-        test::black_box(&buf);
-        unsafe { buf.set_len(0); }
     })
 }
 
@@ -191,7 +79,7 @@ fn from_long_slice(b: &mut Bencher) {
     let data = [0u8; 128];
     b.bytes = data.len() as u64;
     b.iter(|| {
-        let buf = BytesMut::from(&data[..]);
+        let buf = Bytes::copy_from_slice(&data[..]);
         test::black_box(buf);
     })
 }
@@ -217,34 +105,14 @@ fn slice_short_from_arc(b: &mut Bencher) {
     })
 }
 
-// Keep in sync with bytes.rs
-#[cfg(target_pointer_width = "64")]
-const INLINE_CAP: usize = 4 * 8 - 1;
-#[cfg(target_pointer_width = "32")]
-const INLINE_CAP: usize = 4 * 4 - 1;
-
-#[bench]
-fn slice_avg_le_inline_from_arc(b: &mut Bencher) {
-    b.iter(|| {
-        // `clone` is to convert to ARC
-        let b = Bytes::from(vec![17; 1024]).clone();
-        for i in 0..1000 {
-            // [1, INLINE_CAP]
-            let len = 1 + i % (INLINE_CAP - 1);
-            test::black_box(b.slice(i % 10..i % 10 + len));
-        }
-    })
-}
-
 #[bench]
-fn slice_large_le_inline_from_arc(b: &mut Bencher) {
+fn split_off_and_drop(b: &mut Bencher) {
     b.iter(|| {
-        // `clone` is to convert to ARC
-        let b = Bytes::from(vec![17; 1024]).clone();
-        for i in 0..1000 {
-            // [INLINE_CAP - 10, INLINE_CAP]
-            let len = INLINE_CAP - 9 + i % 10;
-            test::black_box(b.slice(i % 10..i % 10 + len));
+        for _ in 0..1024 {
+            let v = vec![10; 200];
+            let mut b = Bytes::from(v);
+            test::black_box(b.split_off(100));
+            test::black_box(b);
         }
     })
 }
diff --git a/benches/bytes_mut.rs b/benches/bytes_mut.rs
@@ -0,0 +1,142 @@
+#![feature(test)]
+#![deny(warnings, rust_2018_idioms)]
+
+extern crate test;
+
+use test::Bencher;
+use bytes::{BufMut, BytesMut};
+
+#[bench]
+fn alloc_small(b: &mut Bencher) {
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(BytesMut::with_capacity(12));
+        }
+    })
+}
+
+#[bench]
+fn alloc_mid(b: &mut Bencher) {
+    b.iter(|| {
+        test::black_box(BytesMut::with_capacity(128));
+    })
+}
+
+#[bench]
+fn alloc_big(b: &mut Bencher) {
+    b.iter(|| {
+        test::black_box(BytesMut::with_capacity(4096));
+    })
+}
+
+
+#[bench]
+fn deref_unique(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(4096);
+    buf.put(&[0u8; 1024][..]);
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_unique_unroll(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(4096);
+    buf.put(&[0u8; 1024][..]);
+
+    b.iter(|| {
+        for _ in 0..128 {
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_shared(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(4096);
+    buf.put(&[0u8; 1024][..]);
+    let _b2 = buf.split_off(1024);
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_two(b: &mut Bencher) {
+    let mut buf1 = BytesMut::with_capacity(8);
+    buf1.put(&[0u8; 8][..]);
+
+    let mut buf2 = BytesMut::with_capacity(4096);
+    buf2.put(&[0u8; 1024][..]);
+
+    b.iter(|| {
+        for _ in 0..512 {
+            test::black_box(&buf1[..]);
+            test::black_box(&buf2[..]);
+        }
+    })
+}
+
+#[bench]
+fn clone_frozen(b: &mut Bencher) {
+    let bytes = BytesMut::from(&b"hello world 1234567890 and have a good byte 0987654321"[..]).split().freeze();
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&bytes.clone());
+        }
+    })
+}
+
+#[bench]
+fn alloc_write_split_to_mid(b: &mut Bencher) {
+    b.iter(|| {
+        let mut buf = BytesMut::with_capacity(128);
+        buf.put_slice(&[0u8; 64]);
+        test::black_box(buf.split_to(64));
+    })
+}
+
+#[bench]
+fn drain_write_drain(b: &mut Bencher) {
+    let data = [0u8; 128];
+
+    b.iter(|| {
+        let mut buf = BytesMut::with_capacity(1024);
+        let mut parts = Vec::with_capacity(8);
+
+        for _ in 0..8 {
+            buf.put(&data[..]);
+            parts.push(buf.split_to(128));
+        }
+
+        test::black_box(parts);
+    })
+}
+
+#[bench]
+fn fmt_write(b: &mut Bencher) {
+    use std::fmt::Write;
+    let mut buf = BytesMut::with_capacity(128);
+    let s = "foo bar baz quux lorem ipsum dolor et";
+
+    b.bytes = s.len() as u64;
+    b.iter(|| {
+        let _ = write!(buf, "{}", s);
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    })
+}
diff --git a/ci/azure-cross-compile.yml b/ci/azure-cross-compile.yml
@@ -1,5 +1,5 @@
 parameters:
-  cmd: test
+  cmd: build
   rust_version: stable
 
 jobs: