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crypto/tls: pool Conn's outBuf to reduce memory cost of idle connections

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Derived from CL 263277, which includes benchmarks.

Fixes #42035

Co-authored-by: Filippo Valsorda <filippo@golang.org>
Change-Id: I5f28673f95d4568b7d13dbc20e9d4b48d481a93d
Reviewed-on: https://go-review.googlesource.com/c/go/+/267957
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Filippo Valsorda <filippo@golang.org>
Trust: Roland Shoemaker <roland@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Roberto Clapis <roberto@golang.org>
This commit is contained in:
cch123 2020-10-19 12:55:46 +00:00 • committed by Filippo Valsorda
parent 5c31c9a8a5
commit f3c794cde3
1 changed files with 27 additions and 9 deletions
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36
conn.go
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@ -94,7 +94,6 @@ type Conn struct {
rawInput bytes.Buffer // raw input, starting with a record header rawInput bytes.Buffer // raw input, starting with a record header
input bytes.Reader // application data waiting to be read, from rawInput.Next input bytes.Reader // application data waiting to be read, from rawInput.Next
hand bytes.Buffer // handshake data waiting to be read hand bytes.Buffer // handshake data waiting to be read
outBuf []byte // scratch buffer used by out.encrypt
buffering bool // whether records are buffered in sendBuf buffering bool // whether records are buffered in sendBuf
sendBuf []byte // a buffer of records waiting to be sent sendBuf []byte // a buffer of records waiting to be sent
@ -928,9 +927,28 @@ func (c *Conn) flush() (int, error) {
return n, err return n, err
} }
// outBufPool pools the record-sized scratch buffers used by writeRecordLocked.
var outBufPool = sync.Pool{
New: func() interface{} {
return new([]byte)
},
}
// writeRecordLocked writes a TLS record with the given type and payload to the // writeRecordLocked writes a TLS record with the given type and payload to the
// connection and updates the record layer state. // connection and updates the record layer state.
func (c *Conn) writeRecordLocked(typ recordType, data []byte) (int, error) { func (c *Conn) writeRecordLocked(typ recordType, data []byte) (int, error) {
outBufPtr := outBufPool.Get().(*[]byte)
outBuf := *outBufPtr
defer func() {
// You might be tempted to simplify this by just passing &outBuf to Put,
// but that would make the local copy of the outBuf slice header escape
// to the heap, causing an allocation. Instead, we keep around the
// pointer to the slice header returned by Get, which is already on the
// heap, and overwrite and return that.
*outBufPtr = outBuf
outBufPool.Put(outBufPtr)
}()
var n int var n int
for len(data) > 0 { for len(data) > 0 {
m := len(data) m := len(data)
@ -938,8 +956,8 @@ func (c *Conn) writeRecordLocked(typ recordType, data []byte) (int, error) {
m = maxPayload m = maxPayload
} }
_, c.outBuf = sliceForAppend(c.outBuf[:0], recordHeaderLen) _, outBuf = sliceForAppend(outBuf[:0], recordHeaderLen)
c.outBuf[0] = byte(typ) outBuf[0] = byte(typ)
vers := c.vers vers := c.vers
if vers == 0 { if vers == 0 {
// Some TLS servers fail if the record version is // Some TLS servers fail if the record version is
@ -950,17 +968,17 @@ func (c *Conn) writeRecordLocked(typ recordType, data []byte) (int, error) {
// See RFC 8446, Section 5.1. // See RFC 8446, Section 5.1.
vers = VersionTLS12 vers = VersionTLS12
} }
c.outBuf[1] = byte(vers >> 8) outBuf[1] = byte(vers >> 8)
c.outBuf[2] = byte(vers) outBuf[2] = byte(vers)
c.outBuf[3] = byte(m >> 8) outBuf[3] = byte(m >> 8)
c.outBuf[4] = byte(m) outBuf[4] = byte(m)
var err error var err error
c.outBuf, err = c.out.encrypt(c.outBuf, data[:m], c.config.rand()) outBuf, err = c.out.encrypt(outBuf, data[:m], c.config.rand())
if err != nil { if err != nil {
return n, err return n, err
} }
if _, err := c.write(c.outBuf); err != nil { if _, err := c.write(outBuf); err != nil {
return n, err return n, err
} }
n += m n += m