http2: reduce frameScratchBuffer caching aggressiveness
Use a sync.Pool, not per ClientConn.
Co-authored with dneil@google.com
Fixes golang/go#38049
Change-Id: I93f06b19857ab495ffcf15d7ed2aaa2a6cb31515
Reviewed-on: https://go-review.googlesource.com/c/net/+/325169
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/http2/transport.go b/http2/transport.go
index 7bd4b9c..b97adff 100644
--- a/http2/transport.go
+++ b/http2/transport.go
@@ -264,9 +264,8 @@
peerMaxHeaderListSize uint64
initialWindowSize uint32
- hbuf bytes.Buffer // HPACK encoder writes into this
- henc *hpack.Encoder
- freeBuf [][]byte
+ hbuf bytes.Buffer // HPACK encoder writes into this
+ henc *hpack.Encoder
wmu sync.Mutex // held while writing; acquire AFTER mu if holding both
werr error // first write error that has occurred
@@ -913,46 +912,6 @@
return cc.closeForError(err)
}
-const maxAllocFrameSize = 512 << 10
-
-// frameBuffer returns a scratch buffer suitable for writing DATA frames.
-// They're capped at the min of the peer's max frame size or 512KB
-// (kinda arbitrarily), but definitely capped so we don't allocate 4GB
-// bufers.
-func (cc *ClientConn) frameScratchBuffer() []byte {
- cc.mu.Lock()
- size := cc.maxFrameSize
- if size > maxAllocFrameSize {
- size = maxAllocFrameSize
- }
- for i, buf := range cc.freeBuf {
- if len(buf) >= int(size) {
- cc.freeBuf[i] = nil
- cc.mu.Unlock()
- return buf[:size]
- }
- }
- cc.mu.Unlock()
- return make([]byte, size)
-}
-
-func (cc *ClientConn) putFrameScratchBuffer(buf []byte) {
- cc.mu.Lock()
- defer cc.mu.Unlock()
- const maxBufs = 4 // arbitrary; 4 concurrent requests per conn? investigate.
- if len(cc.freeBuf) < maxBufs {
- cc.freeBuf = append(cc.freeBuf, buf)
- return
- }
- for i, old := range cc.freeBuf {
- if old == nil {
- cc.freeBuf[i] = buf
- return
- }
- }
- // forget about it.
-}
-
// errRequestCanceled is a copy of net/http's errRequestCanceled because it's not
// exported. At least they'll be DeepEqual for h1-vs-h2 comparisons tests.
var errRequestCanceled = errors.New("net/http: request canceled")
@@ -1295,11 +1254,35 @@
errReqBodyTooLong = errors.New("http2: request body larger than specified content length")
)
+// frameScratchBufferLen returns the length of a buffer to use for
+// outgoing request bodies to read/write to/from.
+//
+// It returns max(1, min(peer's advertised max frame size,
+// Request.ContentLength+1, 512KB)).
+func (cs *clientStream) frameScratchBufferLen(maxFrameSize int) int {
+ const max = 512 << 10
+ n := int64(maxFrameSize)
+ if n > max {
+ n = max
+ }
+ if cl := actualContentLength(cs.req); cl != -1 && cl+1 < n {
+ // Add an extra byte past the declared content-length to
+ // give the caller's Request.Body io.Reader a chance to
+ // give us more bytes than they declared, so we can catch it
+ // early.
+ n = cl + 1
+ }
+ if n < 1 {
+ return 1
+ }
+ return int(n) // doesn't truncate; max is 512K
+}
+
+var bufPool sync.Pool // of *[]byte
+
func (cs *clientStream) writeRequestBody(body io.Reader, bodyCloser io.Closer) (err error) {
cc := cs.cc
sentEnd := false // whether we sent the final DATA frame w/ END_STREAM
- buf := cc.frameScratchBuffer()
- defer cc.putFrameScratchBuffer(buf)
defer func() {
traceWroteRequest(cs.trace, err)
@@ -1318,9 +1301,24 @@
remainLen := actualContentLength(req)
hasContentLen := remainLen != -1
+ cc.mu.Lock()
+ maxFrameSize := int(cc.maxFrameSize)
+ cc.mu.Unlock()
+
+ // Scratch buffer for reading into & writing from.
+ scratchLen := cs.frameScratchBufferLen(maxFrameSize)
+ var buf []byte
+ if bp, ok := bufPool.Get().(*[]byte); ok && len(*bp) >= scratchLen {
+ defer bufPool.Put(bp)
+ buf = *bp
+ } else {
+ buf = make([]byte, scratchLen)
+ defer bufPool.Put(&buf)
+ }
+
var sawEOF bool
for !sawEOF {
- n, err := body.Read(buf[:len(buf)-1])
+ n, err := body.Read(buf[:len(buf)])
if hasContentLen {
remainLen -= int64(n)
if remainLen == 0 && err == nil {
@@ -1331,8 +1329,9 @@
// to send the END_STREAM bit early, double-check that we're actually
// at EOF. Subsequent reads should return (0, EOF) at this point.
// If either value is different, we return an error in one of two ways below.
+ var scratch [1]byte
var n1 int
- n1, err = body.Read(buf[n:])
+ n1, err = body.Read(scratch[:])
remainLen -= int64(n1)
}
if remainLen < 0 {
@@ -1402,10 +1401,6 @@
}
}
- cc.mu.Lock()
- maxFrameSize := int(cc.maxFrameSize)
- cc.mu.Unlock()
-
cc.wmu.Lock()
defer cc.wmu.Unlock()
