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runtime: use hw.ncpuonline sysctl in getncpu on openbsd

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The number of CPUs reported by the hw.ncpu sysctl is twice as high as
the actual number of CPUs running on OpenBSD 6.4. with hyperthreading
disabled (hw.smt=0). Try hw.cpuonline first and fall back to hw.ncpu
in case it fails (which is the case on older OpenBSD before 6.4).

Fixes #30127

Change-Id: Id091234b8038cc9f7c40519d039fc1a05437c40d
Reviewed-on: https://go-review.googlesource.com/c/161757
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Tobias Klauser 2019-02-08 09:25:05 +01:00 committed by Brad Fitzpatrick
parent ea65d015b8
commit c55eeeb718
1 changed files with 12 additions and 6 deletions
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12
src/runtime/os_openbsd.go
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@ -87,6 +87,7 @@ const (
_CTL_HW = 6
_HW_NCPU = 3
_HW_PAGESIZE = 7
_HW_NCPUONLINE = 25
)
func sysctlInt(mib []uint32) (int32, bool) {
@ -100,9 +101,14 @@ func sysctlInt(mib []uint32) (int32, bool) {
}
func getncpu() int32 {
// Fetch hw.ncpu via sysctl.
if ncpu, ok := sysctlInt([]uint32{_CTL_HW, _HW_NCPU}); ok {
return int32(ncpu)
// Try hw.ncpuonline first because hw.ncpu would report a number twice as
// high as the actual CPUs running on OpenBSD 6.4 with hyperthreading
// disabled (hw.smt=0). See https://golang.org/issue/30127
if n, ok := sysctlInt([]uint32{_CTL_HW, _HW_NCPUONLINE}); ok {
return int32(n)
}
if n, ok := sysctlInt([]uint32{_CTL_HW, _HW_NCPU}); ok {
return int32(n)
}
return 1
}