Refactor iterate_meta_bits

Cargo.toml

@@ -75,6 +75,10 @@ perf_counter = ["pfm"]
 # CI scripts run those tests with this feature.
 mock_test = []
 
+# This feature is only used for benchmarks.
+# It will expose some private functions for benchmarking.
+bench = []
+
 # .github/scripts/ci-common.sh extracts features from the following part (including from comments).
 # So be careful when editing or adding stuff to the section below.
 

benches/bulk_meta/bzero_bset.rs

@@ -0,0 +1,62 @@
+//! Benchmarks for bulk zeroing and setting.
+
+use std::os::raw::c_void;
+
+use criterion::Criterion;
+use mmtk::util::{constants::LOG_BITS_IN_WORD, metadata::side_metadata::SideMetadataSpec, Address};
+
+fn allocate_aligned(size: usize) -> Address {
+    let ptr = unsafe {
+        std::alloc::alloc_zeroed(std::alloc::Layout::from_size_align(size, size).unwrap())
+    };
+    Address::from_mut_ptr(ptr)
+}
+
+const LINE_BYTES: usize = 256usize; // Match an Immix line size.
+const BLOCK_BYTES: usize = 32768usize; // Match an Immix block size.
+
+// Asssume one-bit-per-word metadata (matching VO bits).
+const LINE_META_BYTES: usize = LINE_BYTES >> LOG_BITS_IN_WORD;
+const BLOCK_META_BYTES: usize = BLOCK_BYTES >> LOG_BITS_IN_WORD;
+
+pub fn bench(c: &mut Criterion) {
+    c.bench_function("bzero_bset_line", |b| {
+        let start = allocate_aligned(LINE_META_BYTES);
+        let end = start + LINE_META_BYTES;
+
+        b.iter(|| {
+            SideMetadataSpec::bench_set_meta_bits(start, 0, end, 0);
+            SideMetadataSpec::bench_zero_meta_bits(start, 0, end, 0);
+        })
+    });
+
+    c.bench_function("bzero_bset_line_memset", |b| {
+        let start = allocate_aligned(LINE_META_BYTES);
+        let end = start + LINE_META_BYTES;
+
+        b.iter(|| unsafe {
+            libc::memset(start.as_mut_ref() as *mut c_void, 0xff, end - start);
+            libc::memset(start.as_mut_ref() as *mut c_void, 0x00, end - start);
+        })
+    });
+
+    c.bench_function("bzero_bset_block", |b| {
+        let start = allocate_aligned(BLOCK_META_BYTES);
+        let end = start + BLOCK_META_BYTES;
+
+        b.iter(|| {
+            SideMetadataSpec::bench_set_meta_bits(start, 0, end, 0);
+            SideMetadataSpec::bench_zero_meta_bits(start, 0, end, 0);
+        })
+    });
+
+    c.bench_function("bzero_bset_block_memset", |b| {
+        let start = allocate_aligned(BLOCK_META_BYTES);
+        let end = start + BLOCK_META_BYTES;
+
+        b.iter(|| unsafe {
+            libc::memset(start.as_mut_ref() as *mut c_void, 0xff, end - start);
+            libc::memset(start.as_mut_ref() as *mut c_void, 0x00, end - start);
+        })
+    });
+}

benches/bulk_meta/mod.rs

@@ -0,0 +1 @@
+pub mod bzero_bset;

benches/main.rs

@@ -19,11 +19,14 @@ use criterion::Criterion;
 // However, I will just keep these benchmarks here. If we find it not useful, and we do not plan to improve MockVM, we can delete
 // them.
 
+#[cfg(feature = "bench")]
+mod bulk_meta;
+
 #[cfg(feature = "mock_test")]
 mod mock_bench;
 
-pub fn bench_main(_c: &mut Criterion) {
-    #[cfg(feature = "mock_test")]
+#[cfg(feature = "mock_test")]
+pub fn bench_mock(_c: &mut Criterion) {
     match std::env::var("MMTK_BENCH") {
         Ok(bench) => match bench.as_str() {
             "alloc" => mock_bench::alloc::bench(_c),
@@ -33,12 +36,17 @@ pub fn bench_main(_c: &mut Criterion) {
         },
         Err(_) => panic!("Need to name a benchmark by the env var MMTK_BENCH"),
     }
+}
 
-    #[cfg(not(feature = "mock_test"))]
-    {
-        eprintln!("ERROR: Currently there are no benchmarks when the \"mock_test\" feature is not enabled.");
-        std::process::exit(1);
-    }
+pub fn bench_main(_c: &mut Criterion) {
+    // If the "mock_test" feature is enabled, we only run mock test.
+    #[cfg(feature = "mock_test")]
+    return bench_mock(_c);
+
+    // Some benchmarks rely on the "bench" feature to expose some private functions.
+    // Run them with `cargo bench --features bench`.
+    #[cfg(feature = "bench")]
+    bulk_meta::bzero_bset::bench(_c);
 }
 
 criterion_group!(benches, bench_main);