Disabling kernel hw-thread migration/stealing policies allows Ryzen to build lang/ghc (finally!)

[Mark Millard]

[This test was suggesetd by Don Lewis's comment 73
for buugzilla 221029.]

I finally got a Ryzen based build of lang/ghc :

# pkg search ghc
ghc-8.0.2_1                    Compiler for the functional language Haskell

This used as a kernel context with:

sysctl kern.sched.balance=0
sysctl kern.sched.steal_idle=0

and a poudriere context of:

PARALLEL_JOBS=1
ALLOW_MAKE_JOBS=no

and ALLOW_MAKE_JOBS_PACKAGES not having a match
for lang/ghc

The Ryzen was not otherwise loaded with activity
(beyond normal background stuff in a simple
configuration).

(This means that kern.sched.balance=1 might
have worked as it had nothing to do. In fact
I have that test running now.)

By contrast for the kernel context:

sysctl kern.sched.balance=1
sysctl kern.sched.steal_idle=1

the lang/ghc build fails quickly compared to
the somewhat over 1.5 hours it took for a
build to complete.

The detailed build step for the failure tends to
vary from build attempt to build attempt. But they
tend to involve Bus Errors for the failures.


My context here is actually FreeBSD
running as a guest in a VirtualBox
virtual machine --that is running under
Windows 10 Pro . The Ryzen has all 16
threads enabled but Virtual Box is set
to supply 8 "processors" to the virtual
machine (in VirtualBox terminology).
But Poudriere is set to avoid parallel
builds.

Also: Prior build attempts had already
built packages for lang/ghc's
prerequisites. So the experiments here
are just for the lang/ghc related
build activity.

===
Mark Millard
markmi at dsl-only.net