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bradfitz opened this issue Oct 26, 2018 · 4 comments
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x/build/env/openbsd: set sysctl hw.smt=1 #28403

bradfitz opened this issue Oct 26, 2018 · 4 comments
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Builders x/build issues (builders, bots, dashboards) FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. OS-OpenBSD Performance
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@bradfitz
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The OpenBSD images should disable Spectre/Meltdown protections and set sysctl hw.smt=1 per

https://go-review.googlesource.com/c/build/+/144777#message-b10c10646c34b670194db8c9d72ac8a551d3ab80
@bradfitz bradfitz added Performance OS-OpenBSD NeedsFix The path to resolution is known, but the work has not been done. labels Oct 26, 2018
@gopherbot gopherbot added this to the Unreleased milestone Oct 26, 2018
@gopherbot gopherbot added the Builders x/build issues (builders, bots, dashboards) label Oct 26, 2018
@gopherbot
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Change https://golang.org/cl/144777 mentions this issue: dashboard: switch OpenBSD trybot from 6.2 to 6.4

@gopherbot
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Change https://golang.org/cl/145022 mentions this issue: env/openbsd-amd64: enable SMT on OpenBSD 6.4

@bradfitz
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Actually, turns out we can do this at runtime from the buildlet:

buildlet# sysctl hw.smt=1; sysctl hw.ncpuonline 
hw.smt: 1 -> 1
hw.ncpuonline=4

buildlet# sysctl hw.smt=0; sysctl hw.ncpuonline 
hw.smt: 1 -> 0
hw.ncpuonline=2

@dmitshur
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dmitshur commented Oct 26, 2018 •
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For reference, I tried sysctl hw.ncpuonline on a openbsd-386-64 builder, and it reported hw.ncpuonline=4 despite not having hw.smt (compared to amd64 builder which reports hw.ncpuonline=2 until you set hw.smt=1).

I understand that to mean that SMT is not disabled on 32-bit OpenBSD.

@dmitshur dmitshur mentioned this issue Nov 2, 2018
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Builders x/build issues (builders, bots, dashboards) FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. OS-OpenBSD Performance
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