http2: reduce allocations of (*clientConnReadLoop).handleReponse
Reduce allocation by using 1 capacity slices out of a single
pre-allocated slice for header values, similarly to how it is done
in textproto.(*Reader).ReadMIMEHeader.
name old time/op new time/op delta
ClientResponseHeaders/___0_Headers-16 82.3µs ± 7% 76.4µs ± 4% -7.18% (p=0.000 n=10+10)
ClientResponseHeaders/__10_Headers-16 101µs ± 2% 99µs ± 3% -2.00% (p=0.016 n=8+10)
ClientResponseHeaders/_100_Headers-16 213µs ± 2% 202µs ± 4% -4.96% (p=0.000 n=9+9)
ClientResponseHeaders/1000_Headers-16 2.28ms ± 1% 2.15ms ± 2% -5.58% (p=0.000 n=8+10)
name old alloc/op new alloc/op delta
ClientResponseHeaders/___0_Headers-16 4.60kB ± 0% 4.60kB ± 0% ~ (p=0.201 n=10+10)
ClientResponseHeaders/__10_Headers-16 9.01kB ± 0% 8.66kB ± 0% -3.96% (p=0.000 n=10+10)
ClientResponseHeaders/_100_Headers-16 54.4kB ± 0% 48.4kB ± 0% -11.01% (p=0.000 n=10+10)
ClientResponseHeaders/1000_Headers-16 702kB ± 0% 595kB ± 0% -15.28% (p=0.000 n=10+9)
name old allocs/op new allocs/op delta
ClientResponseHeaders/___0_Headers-16 57.0 ± 0% 56.0 ± 0% -1.75% (p=0.000 n=10+10)
ClientResponseHeaders/__10_Headers-16 135 ± 0% 123 ± 0% -8.89% (p=0.000 n=10+10)
ClientResponseHeaders/_100_Headers-16 786 ± 0% 679 ± 0% -13.61% (p=0.000 n=10+10)
ClientResponseHeaders/1000_Headers-16 8.14k ± 0% 7.11k ± 0% -12.65% (p=0.000 n=10+10)
Fixes golang/go#37853
Change-Id: I0bc6d879293a202a2742a06aca0b6dacfae7fc5f
Reviewed-on: https://go-review.googlesource.com/c/net/+/223783
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
diff --git a/http2/transport.go b/http2/transport.go
index 81778be..e4fb025 100644
--- a/http2/transport.go
+++ b/http2/transport.go
@@ -1892,7 +1892,9 @@
return nil, errors.New("malformed response from server: malformed non-numeric status pseudo header")
}
- header := make(http.Header)
+ regularFields := f.RegularFields()
+ strs := make([]string, len(regularFields))
+ header := make(http.Header, len(regularFields))
res := &http.Response{
Proto: "HTTP/2.0",
ProtoMajor: 2,
@@ -1900,7 +1902,7 @@
StatusCode: statusCode,
Status: status + " " + http.StatusText(statusCode),
}
- for _, hf := range f.RegularFields() {
+ for _, hf := range regularFields {
key := http.CanonicalHeaderKey(hf.Name)
if key == "Trailer" {
t := res.Trailer
@@ -1912,7 +1914,18 @@
t[http.CanonicalHeaderKey(v)] = nil
})
} else {
- header[key] = append(header[key], hf.Value)
+ vv := header[key]
+ if vv == nil && len(strs) > 0 {
+ // More than likely this will be a single-element key.
+ // Most headers aren't multi-valued.
+ // Set the capacity on strs[0] to 1, so any future append
+ // won't extend the slice into the other strings.
+ vv, strs = strs[:1:1], strs[1:]
+ vv[0] = hf.Value
+ header[key] = vv
+ } else {
+ header[key] = append(vv, hf.Value)
+ }
}
}
diff --git a/http2/transport_test.go b/http2/transport_test.go
index 64fe1ad..1424f81 100644
--- a/http2/transport_test.go
+++ b/http2/transport_test.go
@@ -3927,11 +3927,15 @@
ct.run()
}
-func benchSimpleRoundTrip(b *testing.B, nHeaders int) {
+func benchSimpleRoundTrip(b *testing.B, nReqHeaders, nResHeader int) {
defer disableGoroutineTracking()()
b.ReportAllocs()
st := newServerTester(b,
func(w http.ResponseWriter, r *http.Request) {
+ for i := 0; i < nResHeader; i++ {
+ name := fmt.Sprint("A-", i)
+ w.Header().Set(name, "*")
+ }
},
optOnlyServer,
optQuiet,
@@ -3946,7 +3950,7 @@
b.Fatal(err)
}
- for i := 0; i < nHeaders; i++ {
+ for i := 0; i < nReqHeaders; i++ {
name := fmt.Sprint("A-", i)
req.Header.Set(name, "*")
}
@@ -4037,10 +4041,17 @@
}
func BenchmarkClientRequestHeaders(b *testing.B) {
- b.Run(" 0 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 0) })
- b.Run(" 10 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 10) })
- b.Run(" 100 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 100) })
- b.Run("1000 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 1000) })
+ b.Run(" 0 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 0, 0) })
+ b.Run(" 10 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 10, 0) })
+ b.Run(" 100 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 100, 0) })
+ b.Run("1000 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 1000, 0) })
+}
+
+func BenchmarkClientResponseHeaders(b *testing.B) {
+ b.Run(" 0 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 0, 0) })
+ b.Run(" 10 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 0, 10) })
+ b.Run(" 100 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 0, 100) })
+ b.Run("1000 Headers", func(b *testing.B) { benchSimpleRoundTrip(b, 0, 1000) })
}
func activeStreams(cc *ClientConn) int {
