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cmd/compile: dedup gclocals at compile time #14983

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skohanim opened this issue Mar 27, 2016 · 5 comments
Closed

cmd/compile: dedup gclocals at compile time #14983

skohanim opened this issue Mar 27, 2016 · 5 comments
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Go1.7

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@skohanim
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Version:

go version devel +4ffa5eb Sun Mar 27 05:31:54 2016 +0000 linux/amd64

Env:

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/shaharko/gopath"
GORACE=""
GOROOT="/home/shaharko/src/go_master"
GOTOOLDIR="/home/shaharko/src/go_master/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build742740600=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"


$ go tool nm pkg/linux_amd64/io.a | grep gclocals | awk '{ print $3 }' |  wc -l
142 # total gclocals
$ go tool nm pkg/linux_amd64/io.a | grep gclocals | awk '{ print $3 }' | uniq | wc -l
38  # unique gclocals

The symbol duplication factor is ~3.5x.
@minux
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minux commented Mar 27, 2016 via email

@skohanim
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Yes the linker will deduplicate but this should be done by the compiler ahead of time.
It would reduce the object file size and make the linker faster. Possibly also reducing the compiler memory usage.

@minux minux changed the title gclocals have duplicate symbols in the object file cmd/compile: dedup gclocals at compile time Mar 27, 2016
@minux minux added this to the Go1.7 milestone Mar 27, 2016
@mwhudson
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Oh wow, I had no idea each .o file contained multiple copies of the gclocals symbols.

@gopherbot
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CL https://golang.org/cl/22293 mentions this issue.

@skohanim
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Nice! Thanks.

@golang golang locked and limited conversation to collaborators Apr 28, 2017
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@minux @mwhudson @gopherbot @skohanim