Use atomic.OrUint32 to set bits in SyncFilter (#11)

This is only enabled for Go 1.24 and up. It would work on 1.23, but then
atomic.OrUint32 would not get intrinsified on amd64, causing a pretty
big performance hit on that platform. Tested and benchmarked with
go1.24-2bffb8b3fb.

Checking whether the bit is already set, i.e.,

	if atomic.LoadUint32(p)&bit == 0 {
		atomic.OrUint32(p, bit)
	}

gives a 3× speedup for tiny Bloom filters (capacity 1e5) but slows
things down at capacity 1e7. We optimize for the larger filters, at
least for now.

    goos: linux
    goarch: amd64
    pkg: github.com/greatroar/blobloom/benchmarks
    cpu: Intel(R) Core(TM) i7-3770K CPU @ 3.50GHz
                 │ benchmarks/old │          benchmarks/check          │           benchmarks/new            │
                 │     sec/op     │   sec/op     vs base               │   sec/op     vs base                │
    Add1e5_1e2-8      14.81n ± 0%   13.99n ± 1%   -5.60% (p=0.002 n=6)   43.58n ± 1%  +194.13% (p=0.002 n=6)
    Add1e6_1e2-8      19.21n ± 1%   19.89n ± 1%   +3.51% (p=0.002 n=6)   47.74n ± 0%  +148.54% (p=0.002 n=6)
    Add1e7_1e2-8     103.70n ± 1%   89.63n ± 1%  -13.56% (p=0.002 n=6)   75.22n ± 2%   -27.47% (p=0.002 n=6)
    Add1e8_1e2-8      135.2n ± 0%   114.8n ± 1%  -15.16% (p=0.002 n=6)   100.9n ± 1%   -25.36% (p=0.002 n=6)
    Add1e5_1e3-8      21.14n ± 1%   19.50n ± 0%   -7.76% (p=0.002 n=6)   66.45n ± 0%  +214.28% (p=0.002 n=6)
    Add1e6_1e3-8      27.99n ± 0%   28.79n ± 1%   +2.82% (p=0.002 n=6)   70.29n ± 0%  +151.06% (p=0.002 n=6)
    Add1e7_1e3-8      149.0n ± 2%   122.3n ± 2%  -17.89% (p=0.002 n=6)   106.1n ± 2%   -28.83% (p=0.002 n=6)
    Add1e8_1e3-8      179.2n ± 0%   141.3n ± 0%  -21.20% (p=0.002 n=6)   125.3n ± 1%   -30.10% (p=0.002 n=6)
    geomean           53.09n        47.91n        -9.76%                 74.80n        +40.90%

.github/workflows/test.yml

@@ -9,12 +9,12 @@ jobs:
   test:
     strategy:
       matrix:
-        goversion: [1.16, 1.19]
+        goversion: [1.16, 1.19, 1.23]
     runs-on: ubuntu-latest
 
     steps:
       - name: Install Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.goversion }}
       - name: Checkout
@@ -39,7 +39,7 @@ jobs:
 
     steps:
       - name: Install Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v4
         with:
           go-version: 1.19
       - name: Install QEMU

sync.go

@@ -127,19 +127,3 @@ func getbitAtomic(b *block, i uint32) bool {
 	x := atomic.LoadUint32(&(*b)[(i/wordSize)%blockWords])
 	return x&bit != 0
 }
-
-// setbit sets bit (i modulo BlockBits) of b, atomically.
-func setbitAtomic(b *block, i uint32) {
-	bit := uint32(1) << (i % wordSize)
-	p := &(*b)[(i/wordSize)%blockWords]
-
-	for {
-		old := atomic.LoadUint32(p)
-		if old&bit != 0 {
-			// Checking here instead of checking the return value from
-			// the CAS is between 50% and 80% faster on the benchmark.
-			return
-		}
-		atomic.CompareAndSwapUint32(p, old, old|bit)
-	}
-}

sync_go124.go

@@ -0,0 +1,27 @@
+// Copyright 2024 the Blobloom authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.24
+// +build go1.24
+
+package blobloom
+
+import "sync/atomic"
+
+// setbit sets bit (i modulo BlockBits) of b, atomically.
+func setbitAtomic(b *block, i uint32) {
+	bit := uint32(1) << (i % wordSize)
+	p := &(*b)[(i/wordSize)%blockWords]
+	atomic.OrUint32(p, bit)
+}

sync_nogo124.go

@@ -0,0 +1,36 @@
+// Copyright 2024 the Blobloom authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !go1.24
+// +build !go1.24
+
+package blobloom
+
+import "sync/atomic"
+
+// setbit sets bit (i modulo BlockBits) of b, atomically.
+func setbitAtomic(b *block, i uint32) {
+	bit := uint32(1) << (i % wordSize)
+	p := &(*b)[(i/wordSize)%blockWords]
+
+	for {
+		old := atomic.LoadUint32(p)
+		if old&bit != 0 {
+			// Checking here instead of checking the return value from
+			// the CAS is between 50% and 80% faster on the benchmark.
+			return
+		}
+		atomic.CompareAndSwapUint32(p, old, old|bit)
+	}
+}