x/net/http2: optimize typeFrameParser using an array

[evanj]

Go version

go version go1.24.2 darwin/arm64

Output of go env in your module/workspace:

AR='ar'
CC='cc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='c++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/evan.jones/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/evan.jones/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/g1/97d8s0r57hj4nv4_qd3fqcrm0000gp/T/go-build274632297=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/evan.jones/go-net/go.mod'
GOMODCACHE='/Users/evan.jones/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/evan.jones/go'
GOPRIVATE=''
GOPROXY=''
GOROOT='/opt/homebrew/Cellar/go/1.24.2/libexec'
GOSUMDB='sum.golang.org'
GOTELEMETRY='on'
GOTELEMETRYDIR='/Users/evan.jones/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.24.2/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.2'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

I have been looking at gRPC overhead using the Go profiler for production services at Datadog. I noticed that http2.typeFrameParser shows up as 0.1% of total CPU for a high QPS service. I have submitted a gerrit code review to optimize this function by replacing the map lookup with an array.

Suggested micro-optimization: https://go-review.googlesource.com/c/net/+/670415

What did you see happen?

The attached screenshot shows the pprof output for a production service, focused on this function. The "0.16% of profile" suggests that this function is 0.16% of all CPU used for this service. The output shows that all the time is the map lookup since the function does not do anything else.

Suggested micro-optimization: https://go-review.googlesource.com/c/net/+/670415

What did you expect to see?

This function will use less CPU with an array lookup.

[gabyhelp]

Related Issues

• x/net/http2: reduce Framer ReadFrame allocations #18502 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[gopherbot]

Change https://go.dev/cl/670415 mentions this issue: http2: use an array instead of a map in typeFrameParser

[cherrymui]

cc @neild @tombergan