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sminf opened this issue May 1, 2021 · 6 comments
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cmd/compile: run out of memory during -N -l compilation #45897

sminf opened this issue May 1, 2021 · 6 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.

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@sminf
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sminf commented May 1, 2021 •
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What version of Go are you using (go version)?

$ go version
go version go1.16.3 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/user/.cache/go-build"
GOENV="/home/user/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/user/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/user/go"
GOPRIVATE=""
GOPROXY="direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.3"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1710213132=/tmp/go-build -gno-record-gcc-switches"

What did you do?

main.go

package main

import (
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/text"
)

func main() {
	parser := goldmark.DefaultParser()
	parser.Parse(text.NewReader([]byte(``)))
}

go.mod

module playground

go 1.16

require github.com/yuin/goldmark v1.3.5 // indirect

build main.go with gcflags all=-N -l

$ go build -gcflags "all=-N -l" main.go

What did you expect to see?

Successfully built.

What did you see instead?

$ go build -gcflags "all=-N -l" main.go
go build github.com/yuin/goldmark/util: /usr/lib/go/pkg/tool/linux_amd64/compile: signal: killed

I notice memory have ran out, and I have 10GB free memory before building.
@davecheney
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Can you please check dmesg and post the entire output of the OOM killer. Thank you

@sminf
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sminf commented May 1, 2021

dmesg.log

@davecheney
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5.2gb rss does seem excessive.

@davecheney davecheney changed the title cmd/compile: run out of memory during compilation cmd/compile: run out of memory during -N -l compilaiton May 1, 2021
@davecheney davecheney changed the title cmd/compile: run out of memory during -N -l compilaiton cmd/compile: run out of memory during -N -l compilation May 1, 2021
@ALTree ALTree added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label May 1, 2021
@randall77
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Likely this is compiling github.com/yuin/goldmark@v1.3.5/util/html5entities.go which is a big map with complicated entries.
I can compile using about 3GB on my machine. Not sure why it goes to 5+GB for you, but yes, that seems overkill.
Without -N -l it takes under 200MB. In particular, -N is the culprit.

Probably a dup of #41058 .
Also see #37741 for another instance of this code causing trouble :(

Looks like lots of time+space spent in regalloc. The liveness maps get really big. (~30K blocks, ~5K live values per block.) Maybe there's something we could do here. Turn on some processing that's normally off with -N when functions are big, or something like that. Maybe there's also a tweak to map building that could trim liveness (e.g. a VarKill in the right spot).
Improving regalloc to make it not use quadratic space would be even better, but that's not easy.

@randall77
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Looks like the O(n^2) behavior comes from putting constant expressions in the entry block and not CSEing or tightening them.
The entry block contains lots of things like:

v650 (?) = LEAQ <*uint8> {type.[1]int} v3
v789 (?) = LEAQ <*uint8> {type.[1]int} v3
v913 (?) = LEAQ <*uint8> {type.[1]int} v3

One for each allocation in the map literal (the code in question allocates a [1]int as part of the map entry). They are all only used for a single map assignment. At the first map entry assignment, they are all live.

@gopherbot
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Change https://golang.org/cl/316369 mentions this issue: cmd/compile: when compiling with -N, avoid entry block

@ALTree ALTree added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels May 3, 2021
@golang golang locked and limited conversation to collaborators May 4, 2022
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@davecheney @ALTree @randall77 @gopherbot @sminf