adds an atomic variant of the bloom filter (#12422)

For crds_gossip_pull, we want to parallelize build_crds_filters, which
requires concurrent writes to bloom filters.

This commit implements a variant of the bloom filter which uses atomics
for its bits vector and so is thread-safe.

runtime/benches/bloom.rs

@@ -3,7 +3,8 @@
 extern crate test;
 use bv::BitVec;
 use fnv::FnvHasher;
-use solana_runtime::bloom::{Bloom, BloomHashIndex};
+use rand::Rng;
+use solana_runtime::bloom::{AtomicBloom, Bloom, BloomHashIndex};
 use solana_sdk::{
     hash::{hash, Hash},
     signature::Signature,
@@ -97,3 +98,48 @@ fn bench_sigs_hashmap(bencher: &mut Bencher) {
     });
     assert_eq!(falses, 0);
 }
+
+#[bench]
+fn bench_add_hash(bencher: &mut Bencher) {
+    let mut rng = rand::thread_rng();
+    let hash_values: Vec<_> = std::iter::repeat_with(|| Hash::new_rand(&mut rng))
+        .take(1200)
+        .collect();
+    let mut fail = 0;
+    bencher.iter(|| {
+        let mut bloom = Bloom::random(1287, 0.1, 7424);
+        for hash_value in &hash_values {
+            bloom.add(hash_value);
+        }
+        let index = rng.gen_range(0, hash_values.len());
+        if !bloom.contains(&hash_values[index]) {
+            fail += 1;
+        }
+    });
+    assert_eq!(fail, 0);
+}
+
+#[bench]
+fn bench_add_hash_atomic(bencher: &mut Bencher) {
+    let mut rng = rand::thread_rng();
+    let hash_values: Vec<_> = std::iter::repeat_with(|| Hash::new_rand(&mut rng))
+        .take(1200)
+        .collect();
+    let mut fail = 0;
+    bencher.iter(|| {
+        let bloom: AtomicBloom<_> = Bloom::random(1287, 0.1, 7424).into();
+        // Intentionally not using parallelism here, so that this and above
+        // benchmark only compare the bit-vector ops.
+        // For benchmarking the parallel code, change bellow for loop to:
+        //     hash_values.par_iter().for_each(|v| bloom.add(v));
+        for hash_value in &hash_values {
+            bloom.add(hash_value);
+        }
+        let bloom: Bloom<_> = bloom.into();
+        let index = rng.gen_range(0, hash_values.len());
+        if !bloom.contains(&hash_values[index]) {
+            fail += 1;
+        }
+    });
+    assert_eq!(fail, 0);
+}