adds LRU cache with lazy eviction

Cargo.toml

@@ -19,5 +19,9 @@ nightly = ["hashbrown", "hashbrown/nightly"]
 hashbrown = { version = "0.12", optional = true }
 
 [dev-dependencies]
+rand = "0.8.5"
 scoped_threadpool = "0.1.*"
 stats_alloc = "0.1.*"
+
+[[bench]]
+name = "benchmarks"

benches/benchmarks.rs

@@ -0,0 +1,78 @@
+#![feature(test)]
+
+extern crate core;
+extern crate lru;
+extern crate rand;
+extern crate test;
+
+use core::num::NonZeroUsize;
+use rand::Rng;
+use test::Bencher;
+
+const REPS: usize = 1 << 10;
+const NUM_KEYS: usize = 1 << 20;
+const CAPACITY: NonZeroUsize = unsafe { NonZeroUsize::new_unchecked(1 << 17) };
+
+macro_rules! impl_put_bench {
+    ($name: ident, $cache: ty) => {
+        fn $name(bencher: &mut Bencher, capacity: NonZeroUsize, num_keys: usize, reps: usize) {
+            let mut rng = rand::thread_rng();
+            let mut cache = <$cache>::new(capacity);
+            for _ in 0..5 * capacity.get() {
+                let key = rng.gen_range(0..num_keys);
+                let _ = cache.put(key, ());
+            }
+            bencher.iter(|| {
+                for _ in 0..reps {
+                    let key = rng.gen_range(0..num_keys);
+                    let _ = cache.put(key, ());
+                }
+            });
+        }
+    };
+}
+
+macro_rules! impl_get_bench {
+    ($name: ident, $cache: ty) => {
+        fn $name(bencher: &mut Bencher, capacity: NonZeroUsize, num_keys: usize, reps: usize) {
+            let mut rng = rand::thread_rng();
+            let mut cache = <$cache>::new(capacity);
+            for _ in 0..5 * capacity.get() {
+                let key = rng.gen_range(0..num_keys);
+                let _ = cache.put(key, ());
+            }
+            bencher.iter(|| {
+                for _ in 0..reps {
+                    let key = rng.gen_range(0..num_keys);
+                    let _ = cache.get(&key);
+                }
+            });
+        }
+    };
+}
+
+impl_put_bench!(run_put_bench, lru::LruCache<usize, ()>);
+impl_put_bench!(run_put_bench_lazy, lru::lazy::LruCache<usize, ()>);
+
+impl_get_bench!(run_get_bench, lru::LruCache<usize, ()>);
+impl_get_bench!(run_get_bench_lazy, lru::lazy::LruCache<usize, ()>);
+
+#[bench]
+fn bench_put(bencher: &mut Bencher) {
+    run_put_bench(bencher, CAPACITY, NUM_KEYS, REPS);
+}
+
+#[bench]
+fn bench_put_lazy(bencher: &mut Bencher) {
+    run_put_bench_lazy(bencher, CAPACITY, NUM_KEYS, REPS);
+}
+
+#[bench]
+fn bench_get(bencher: &mut Bencher) {
+    run_get_bench(bencher, CAPACITY, NUM_KEYS, REPS);
+}
+
+#[bench]
+fn bench_get_lazy(bencher: &mut Bencher) {
+    run_get_bench_lazy(bencher, CAPACITY, NUM_KEYS, REPS);
+}