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maps: Equal should not allocate on the heap #65329

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BrannonKing opened this issue Jan 27, 2024 · 3 comments
Closed

maps: Equal should not allocate on the heap #65329

BrannonKing opened this issue Jan 27, 2024 · 3 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Performance WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.

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@BrannonKing
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BrannonKing commented Jan 27, 2024 •
edited

Go version

go1.21.6 linux/amd64

Output of go env in your module/workspace:

GO111MODULE='on'
GOARCH='amd64'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/go'
GOSUMDB='sum.golang.org'
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/lib/go/pkg/tool/linux_amd64'
GOVERSION='go1.21.6'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/brannon/Documents/Research/jobshop_go/go.mod'
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 -ffile-prefix-map=/tmp/go-build2066541701=/tmp/go-build -gno-record-gcc-switches'

What did you do?

Ran the memory profiler for my application.

What did you see happen?

I saw that frequently iterating through a map with type map[uint16]uint32 was causing memory pressure. maps.Equal performs an iteration on one map and indexes into the other.
image

What did you expect to see?

I expected to be able to iterate over a map without allocating on the heap. Surely we can make maps.Equal not allocate on the heap. It seems that stepping through the bucket list shouldn't require a nondeterministic amount of memory.
@seankhliao seankhliao changed the title map iterator should not allocate on the heap maps: Equal should not allocate on the heap Jan 27, 2024
@seankhliao
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can you please provide a minimal reproducer for the issue

@seankhliao seankhliao added Performance NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jan 27, 2024
@BrannonKing
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BrannonKing commented Jan 27, 2024 •
edited

provide a minimal reproducer

I just tried to reproduce it. I cannot reproduce it in any simple scenario. The code that fails will be open source in several months. I'll try to follow up on this then.

@seankhliao seankhliao added the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Jan 27, 2024
@gopherbot
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Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)

@gopherbot gopherbot closed this as not planned Won't fix, can't repro, duplicate, stale Feb 27, 2024
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