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net/http: server optimization; reduce GCs, generate ~half the garbage

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There was another bufio.Writer not being reused, found with
GOGC=off and -test.memprofile.

benchmark                               old ns/op    new ns/op    delta
BenchmarkServerFakeConnWithKeepAlive        18270        16046  -12.17%

benchmark                              old allocs   new allocs    delta
BenchmarkServerFakeConnWithKeepAlive           38           36   -5.26%

benchmark                               old bytes    new bytes    delta
BenchmarkServerFakeConnWithKeepAlive         4598         2488  -45.89%

Update #5100

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/8038047
This commit is contained in:
Brad Fitzpatrick 2013-03-27 13:35:49 -07:00
parent 584a66b785
commit 393b3b1304
1 changed files with 21 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/pkg/net/http/server.go
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@ -281,6 +281,7 @@ type response struct {
w *bufio.Writer // buffers output in chunks to chunkWriter
cw *chunkWriter
sw *switchWriter // of the bufio.Writer, for return to putBufioWriter
// handlerHeader is the Header that Handlers get access to,
// which may be retained and mutated even after WriteHeader.
@ -381,7 +382,7 @@ func (srv *Server) newConn(rwc net.Conn) (c *conn, err error) {
c.sr = liveSwitchReader{r: c.rwc}
c.lr = io.LimitReader(&c.sr, noLimit).(*io.LimitedReader)
br, sr := newBufioReader(c.lr)
bw, sw := newBufioWriter(c.rwc)
bw, sw := newBufioWriterSize(c.rwc, 4<<10)
c.buf = bufio.NewReadWriter(br, bw)
c.bufswr = sr
c.bufsww = sw
@ -402,10 +403,21 @@ type bufioWriterPair struct {
// TODO: use a sync.Cache instead
var (
bufioReaderCache = make(chan bufioReaderPair, 4)
bufioWriterCache = make(chan bufioWriterPair, 4)
bufioReaderCache = make(chan bufioReaderPair, 4)
bufioWriterCache2k = make(chan bufioWriterPair, 4)
bufioWriterCache4k = make(chan bufioWriterPair, 4)
)
func bufioWriterCache(size int) chan bufioWriterPair {
switch size {
case 2 << 10:
return bufioWriterCache2k
case 4 << 10:
return bufioWriterCache4k
}
return nil
}
func newBufioReader(r io.Reader) (*bufio.Reader, *switchReader) {
select {
case p := <-bufioReaderCache:
@ -429,14 +441,14 @@ func putBufioReader(br *bufio.Reader, sr *switchReader) {
}
}
func newBufioWriter(w io.Writer) (*bufio.Writer, *switchWriter) {
func newBufioWriterSize(w io.Writer, size int) (*bufio.Writer, *switchWriter) {
select {
case p := <-bufioWriterCache:
case p := <-bufioWriterCache(size):
p.sw.Writer = w
return p.bw, p.sw
default:
sw := &switchWriter{w}
return bufio.NewWriter(sw), sw
return bufio.NewWriterSize(sw, size), sw
}
}
@ -454,7 +466,7 @@ func putBufioWriter(bw *bufio.Writer, sw *switchWriter) {
}
sw.Writer = nil
select {
case bufioWriterCache <- bufioWriterPair{bw, sw}:
case bufioWriterCache(bw.Available()) <- bufioWriterPair{bw, sw}:
default:
}
}
@ -540,7 +552,7 @@ func (c *conn) readRequest() (w *response, err error) {
cw: new(chunkWriter),
}
w.cw.res = w
w.w = bufio.NewWriterSize(w.cw, bufferBeforeChunkingSize)
w.w, w.sw = newBufioWriterSize(w.cw, bufferBeforeChunkingSize)
return w, nil
}
@ -802,6 +814,7 @@ func (w *response) finishRequest() {
}
w.w.Flush()
putBufioWriter(w.w, w.sw)
w.cw.close()
w.conn.buf.Flush()