On 2019/02/08 19:12, Marc Espie wrote:
> On Fri, Feb 08, 2019 at 12:10:02AM -0500, Ted Unangst wrote:
> > Go tries to use NCPU cpus. Unfortunately, half of them are turned off
> > because
> > hw.smt=0 by default, and then go spends a lot of time fighting against
> > itself.
> >
> > The diff below, against go/src/runtime, changes to use the number of CPUs
> > online. It's possible for this number to change, and thus become stale, but
> > that's unlikely, and not the default.
> >
> > (This sysctl was added in 6.4.)
> >
> > --- os_openbsd.go.orig Fri Feb 8 00:02:27 2019
> > +++ os_openbsd.go Fri Feb 8 00:06:21 2019
> > @@ -85,8 +85,8 @@
> > _KERN_OSREV = 3
> >
> > _CTL_HW = 6
> > - _HW_NCPU = 3
> > _HW_PAGESIZE = 7
> > + _HW_NCPUONLINE = 25
> > )
> >
> > func sysctlInt(mib []uint32) (int32, bool) {
> > @@ -101,7 +101,7 @@
> >
> > func getncpu() int32 {
> > // Fetch hw.ncpu via sysctl.
> > - if ncpu, ok := sysctlInt([]uint32{_CTL_HW, _HW_NCPU}); ok {
> > + if ncpu, ok := sysctlInt([]uint32{_CTL_HW, _HW_NCPUONLINE}); ok {
> > return int32(ncpu)
> > }
> > return 1
IIRC upstream had some requirement for supporting the previous OS version
for their builders, so might be better to have fallback code in case
_HW_NCPUONLINE isn't available.
> Is there at least a knob to turn that off entirely ?
>
> Like, specifically, when you are bulk-building ports, you do not want go
> to hog on every cpu while it's not alone.
>
> Parallelizing everything is not always (very often not actually) a win.
On 2019/02/08 19:55, Otto Moerbeek wrote:
> The GOMACPROCS env var is what you're looking for. If you set it to 1
> go will use 1 core at max.
There are two different things.
go.port.mk's build command line (used for some but not all ports) calls
"go install -p ${MAKE_JOBS}", that controls how many parallel processes
are used. (some like sysutils/prometheus use a different build system).
GOMAXPROCS (X not C) is different - number of threads within one process.
So if both are in play maybe you get N(smp_cores) processes * N(smp_cores)
threads ...
