What version of Go are you using (go version)?
$ go version
go version devel go1.21-56a14ad4bc Wed Feb 1 10:06:08 2023 +0000 linux/amd64
Does this issue reproduce with the latest release?
Yes (go1.20)
What operating system and processor architecture are you using (go env)?
go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/hugo/.cache/go-build"
GOENV="/home/hugo/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/hugo/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/hugo/go"
GOPRIVATE=""
GOPROXY="direct"
GOROOT="/home/hugo/k/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/hugo/k/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="devel go1.21-56a14ad4bc Wed Feb 1 10:06:08 2023 +0000"
GCCGO="gccgo"
GOAMD64="v3"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build992780592=/tmp/go-build -gno-record-gcc-switches"
What did you do?
I have a program which downloads at 2.5Gbit/s from ~12 stream concurrently and runs GC more often than I like.
After some profiling I see:
ROUTINE ======================== crypto/tls.(*Conn).readFromUntil in /home/hugo/k/go/src/crypto/tls/conn.go
2274297 2274449 (flat, cum) 49.80% of Total
. . 801:func (c *Conn) readFromUntil(r io.Reader, n int) error {
. . 802: if c.rawInput.Len() >= n {
. . 803: return nil
. . 804: }
. . 805: needs := n - c.rawInput.Len()
. . 806: // There might be extra input waiting on the wire. Make a best effort
. . 807: // attempt to fetch it so that it can be used in (*Conn).Read to
. . 808: // "predict" closeNotify alerts.
. 152 809: c.rawInput.Grow(needs + bytes.MinRead)
2274297 2274297 810: _, err := c.rawInput.ReadFrom(&atLeastReader{r, int64(needs)})
. . 811: return err
. . 812:}
What did you expect to see?
HTTP1 is a simple protocol, I expect calls to .Read to be allocation free (after buffers have been grown). Either work inplace with the buffer passed in, or by caching buffers.
What did you see instead?
The TLS implementation seems to allocate this atLeastReader pointer very often (on each Read ?).
What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
Yes (
go1.20)What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
I have a program which downloads at 2.5Gbit/s from ~12 stream concurrently and runs GC more often than I like.
After some profiling I see:
What did you expect to see?
HTTP1 is a simple protocol, I expect calls to
.Readto be allocation free (after buffers have been grown). Either work inplace with the buffer passed in, or by caching buffers.What did you see instead?
The TLS implementation seems to allocate this
atLeastReaderpointer very often (on each Read ?).