cmd/link: binary size increase with Go 1.26

[pgimalac]

Go version

1.26rc2

Output of go env in your module/workspace:

AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE='auto'
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/pierre.gimalac/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/pierre.gimalac/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/zp/m8h1x16s30g3f656sxsdt7rm0000gp/T/go-build2439715533=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/pierre.gimalac/pgimalac/kubernetes/go.mod'
GOMODCACHE='/Users/pierre.gimalac/go/pkg/mod'
GONOPROXY=''
GONOSUMDB='github.com/DataDog,go.ddbuild.io'
GOOS='darwin'
GOPATH='/Users/pierre.gimalac/go'
GOPRIVATE=''
GOPROXY='https://depot-read-api-go.us1.ddbuild.io/magicmirror/magicmirror/@current,https://depot-read-api-go.us1.ddbuild.io/magicmirror/testing/@current,proxy.golang.org,direct'
GOROOT='/Users/pierre.gimalac/sdk/go1.26rc2'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/pierre.gimalac/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='go1.26rc2'
GOTOOLDIR='/Users/pierre.gimalac/sdk/go1.26rc2/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.26rc2'
GOWORK='/Users/pierre.gimalac/pgimalac/kubernetes/go.work'
PKG_CONFIG='pkg-config'

What did you do?

I tried building various binaries with go 1.25.6 and go 1.26rc2, and consistently observed a non-negligible (between 300kiB and 1.3MiB) binary size increase, mostly proportional to code size, for binaries ranging from 20MiB to 100MiB.

#77049 (comment) (cc @cherrymui) mentions a fixed 300kiB increase, which is not what I observed.

a small (~300K) fixed-size increase, not proportional to user code size.

I mostly want to ensure this size increase is known/expected (it's not really a blocker for me in practice) as it doesn't match what was mentioned in the other issue.

What did you see happen?

For kubernetes binaries (darwin/arm64):

Binary	Go 1.25.6	Go 1.26rc2	Delta
kube-apiserver	77.9 MiB	78.9 MiB	+1081 KiB
kube-controller-manager	64.6 MiB	65.6 MiB	+1031 KiB
kube-proxy	38.3 MiB	39.1 MiB	+853 KiB
kube-scheduler	43.7 MiB	44.5 MiB	+886 KiB
kubelet	48.5 MiB	49.4 MiB	+982 KiB

If you want to reproduce:

git clone https://github.com/kubernetes/kubernetes.git
cd kubernetes
go get google.golang.org/protobuf@cb6ac5a # fix https://github.com/golang/protobuf/issues/1704
go work vendor
GOTOOLCHAIN=go1.26rc2 make kube-apiserver kubelet kube-controller-manager kube-scheduler kube-proxy
ls -l _output/bin/

For datadog-agent binaries (linux/arm64):

Binary	Go 1.25.6	Go 1.26rc2	Delta
agent	102.2 MiB	103.5 MiB	+1356 KiB
process-agent	31.1 MiB	31.7 MiB	+589 KiB
security-agent	28.8 MiB	29.2 MiB	+461 KiB
system-probe	56.5 MiB	57.5 MiB	+973 KiB
trace-agent	20.9 MiB	21.2 MiB	+334 KiB

What did you expect to see?

A smaller size increase, or ideally none at all.

[gabyhelp]

Related Issues

• all: binaries too big and growing #6853
• cmd/link: slow link times with large amounts of DWARF data #75508
• cmd/link: binary on darwin takes up more space on disk #39044 (closed)
• all: increased toolchain binary sizes #70699 (closed)
• runtime, cmd/compile: between Go1.25.5 and GoTip, with same generated ASM, document binary size increase for very small programs #77049 (closed)
• all: understand binary size changes vs 1.14 #38694
• cmd/go: Go 1.11 stripped binaries 12% larger that Go 1.10 #27784 (closed)
• cmd/compile: binary size increase from generics #70045 (closed)
• all: increased toolchain binary sizes #68109 (closed)

Related Code Changes

• cmd/compile,link: use "go.." for compiler genereated types

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

[egonelbre]

I did a quick goda weight-diff for kube-apiserver:

.../kubernetes/kubernetes/cmd/kube-apiserver ∫ goda weight-diff -h --minimum 10000 kube-apiserver kube-apiserver.126
name                                                             diff       kube-apiserver    kube-apiserver.126
crypto/internal/fips140/drbg.memory+8MB                          8.0MB      -                 8.0MB
crypto/internal/fips140/drbg.memory                              8.0MB      -                 8.0MB
crypto/internal/fips140/drbg.memory+16MB                         8.0MB      -                 8.0MB
crypto/internal/fips140/drbg.memory+24MB                         8.0MB      -                 8.0MB
runtime.pclntab+32MB                                             4.9MB      -                 4.9MB
go:func.*                                                        4.3MB      4.4MB             49.8KB
runtime.functab+8MB                                              158.2KB    4.2MB             4.3MB
_go:funcdescrel                                                  56.5KB     -                 56.5KB
go:funcrel.*                                                     55.7KB     55.7KB            -
k8s.io/kubernetes/pkg/generated/openapi.GetOpenAPIDefinitions    36.9KB     216.2KB           253.1KB
typerel.*+8MB                                                    35.0KB     2.1MB             2.1MB
_go:funcdesc                                                     18.0KB     -                 18.0KB
runtime.pclntab+24MB                                             13.4KB     3.6MB             3.6MB
runtime.epclntab                                                 13.0KB     13.1KB            161B
__cgo_yield                                                      12.5KB     14.9KB            2.3KB
internal/strconv.pow10Tab                                        10.9KB     -                 10.9KB
strconv.detailedPowersOfTen                                      10.9KB     10.9KB            -

It looks like a major increase seems to come from crypto/internal/fips140/drbg.memory which is of type ScratchBuffer [1 << 25]byte. This was added in https://go-review.googlesource.com/c/go/+/703015

Note I did a straight go build in the folder rather than using the makefile.

[cherrymui]

crypto/internal/fips140/drbg.memory

This is a BSS symbol, which should not increase on-disk binary sizes.

[egonelbre]

I just realized that as well. Sorry, for the noise.

[DanielMorsing]

the ScratchBuffer symbol has been picked up by our binary size benchmarks since it got introduced, so we don't have the progression for the size (see performance dashboard), but given the measurements from before it was introduced, I don't expect them to be much different.

I have a fix for the benchmarks here