flate: Improve speed in big stateless blocks. (#718)

* flate: Improve speed in big stateless blocks. Don't re-alloc and copy dict for every block when compressing more than 32KB. ``` benchmark old ns/op new ns/op delta BenchmarkEncodeDigitsSL1e4-32 52954 52850 -0.20% BenchmarkEncodeDigitsSL1e5-32 781061 745420 -4.56% BenchmarkEncodeDigitsSL1e6-32 8143640 7715674 -5.26% BenchmarkEncodeTwainSL1e4-32 68150 68415 +0.39% BenchmarkEncodeTwainSL1e5-32 715140 687326 -3.89% BenchmarkEncodeTwainSL1e6-32 7718175 7339694 -4.90% benchmark old MB/s new MB/s speedup BenchmarkEncodeDigitsSL1e4-32 188.84 189.21 1.00x BenchmarkEncodeDigitsSL1e5-32 128.03 134.15 1.05x BenchmarkEncodeDigitsSL1e6-32 122.80 129.61 1.06x BenchmarkEncodeTwainSL1e4-32 146.74 146.17 1.00x BenchmarkEncodeTwainSL1e5-32 139.83 145.49 1.04x BenchmarkEncodeTwainSL1e6-32 129.56 136.25 1.05x benchmark old allocs new allocs delta BenchmarkEncodeDigitsSL1e4-32 0 0 +0.00% BenchmarkEncodeDigitsSL1e5-32 3 0 -100.00% BenchmarkEncodeDigitsSL1e6-32 41 0 -100.00% BenchmarkEncodeTwainSL1e4-32 0 0 +0.00% BenchmarkEncodeTwainSL1e5-32 3 0 -100.00% BenchmarkEncodeTwainSL1e6-32 41 0 -100.00% benchmark old bytes new bytes delta BenchmarkEncodeDigitsSL1e4-32 0 0 +0.00% BenchmarkEncodeDigitsSL1e5-32 92929 9 -99.99% BenchmarkEncodeDigitsSL1e6-32 1298964 97 -99.99% BenchmarkEncodeTwainSL1e4-32 0 0 +0.00% BenchmarkEncodeTwainSL1e5-32 92928 8 -99.99% BenchmarkEncodeTwainSL1e6-32 1298871 92 -99.99% ``` * Pin garble to v0.7.2
klauspost · Dec 19, 2022 · b3140ce · b3140ce
1 parent 1f355e8
commit b3140ce
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Showing 4 changed files with 19 additions and 6 deletions.
diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
@@ -85,7 +85,7 @@ jobs:
       run: go build github.com/klauspost/compress/s2/cmd/s2c && go build github.com/klauspost/compress/s2/cmd/s2d&&./s2c -verify s2c &&./s2d s2c.s2&&rm ./s2c&&rm s2d&&rm s2c.s2
 
     - name: install garble
-      run: go install mvdan.cc/garble@v0.7.0
+      run: go install mvdan.cc/garble@v0.7.2
 
     - name: goreleaser deprecation
       run: curl -sfL https://git.io/goreleaser | VERSION=v1.9.2 sh -s -- check

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
@@ -21,7 +21,7 @@ jobs:
           go-version: 1.19.x
       -
         name: install garble
-        run: go install mvdan.cc/garble@v0.7.1
+        run: go install mvdan.cc/garble@v0.7.2
       -
         name: Run GoReleaser
         uses: goreleaser/goreleaser-action@v2

diff --git a/.goreleaser.yml b/.goreleaser.yml
@@ -3,7 +3,7 @@
 before:
   hooks:
     - ./gen.sh
-    - go install mvdan.cc/garble@latest
+    - go install mvdan.cc/garble@v0.7.2
 
 builds:
   -

diff --git a/flate/stateless.go b/flate/stateless.go
@@ -86,11 +86,19 @@ func StatelessDeflate(out io.Writer, in []byte, eof bool, dict []byte) error {
 		dict = dict[len(dict)-maxStatelessDict:]
 	}
 
+	// For subsequent loops, keep shallow dict reference to avoid alloc+copy.
+	var inDict []byte
+
 	for len(in) > 0 {
 		todo := in
-		if len(todo) > maxStatelessBlock-len(dict) {
+		if len(inDict) > 0 {
+			if len(todo) > maxStatelessBlock-maxStatelessDict {
+				todo = todo[:maxStatelessBlock-maxStatelessDict]
+			}
+		} else if len(todo) > maxStatelessBlock-len(dict) {
 			todo = todo[:maxStatelessBlock-len(dict)]
 		}
+		inOrg := in
 		in = in[len(todo):]
 		uncompressed := todo
 		if len(dict) > 0 {
@@ -102,7 +110,11 @@ func StatelessDeflate(out io.Writer, in []byte, eof bool, dict []byte) error {
 			todo = combined
 		}
 		// Compress
-		statelessEnc(&dst, todo, int16(len(dict)))
+		if len(inDict) == 0 {
+			statelessEnc(&dst, todo, int16(len(dict)))
+		} else {
+			statelessEnc(&dst, inDict[:maxStatelessDict+len(todo)], maxStatelessDict)
+		}
 		isEof := eof && len(in) == 0
 
 		if dst.n == 0 {
@@ -119,7 +131,8 @@ func StatelessDeflate(out io.Writer, in []byte, eof bool, dict []byte) error {
 		}
 		if len(in) > 0 {
 			// Retain a dict if we have more
-			dict = todo[len(todo)-maxStatelessDict:]
+			inDict = inOrg[len(uncompressed)-maxStatelessDict:]
+			dict = nil
 			dst.Reset()
 		}
 		if bw.err != nil {