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On Mon, Feb 10, 2014 at 09:45:42AM -0600, Tim Daneliuk wrote:
> >>Well ... it has to hit the disk sooner or later. But, if the
> >>frequency of physical writes is low because of aggregated
> >>IO from the cache, I guess that would tend to make the whole
> >>business more CPU bound than IO bound. I just found this surprising.
> >>
> >
> >What is the underlying filesystem?
> >
>=20
> UFS w/Softupdates, no journaling.
>=20
>=20
> [...]
> >>Yeah, I wonder what other people are seeing for a full buildworld/kerne=
l and/or what
> >>the master machines at FreeBSD.org do in this regards.
> >>
> >>Would anyone else care to share with the class?
> >>
> >
> >If you mean "what do the machines do with regard to tuning", the only
> >specific tuning is turning off atime.
> >
>=20
>=20
> Could you comment a bit more about this please? How you do it,
> rationale', etc.
>=20
Each build happens in its own ZFS dataset, so atime is disabled during
dataset creation (zfs create -o atime=3Doff zroot/11-amd64-GENERIC-snap).
The tuning(7) manual has more details, but basically each time a file is
read, a separate write happens to update the file access time. Turning
off atime eliminates these excessive writes.
> >If you mean "what do the machines do as far as overall build time", with
> >a clean obj/ directory, 35 minutes sounds about right. I do not have
> >exact numbers.
> >
> >The machine that currently produces weekly snapshot images uses '-j10'
> >for buildworld and '-j6' for buildkernel for each build. It also runs
> >the builds in parallel. Even with three parallel 'make -j10 buildworld'
> >(one for head/, stable/10/, and stable/9/), disk IO is minimal. The
> >only time the disk IO becomes a bottleneck is when creating the
> >distribution files (base.txz, kernel.txz, etc.).
>=20
>=20
> What sort of CPU/Mem/Disk is that machine?
>=20
This machine is 48-core (4 x 12 cores) Opteron 6174 (2.2GHz), 128GB RAM,
with 5 drives in a raidz1 on a PERC H700 controller.
Glen
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