compiling on nfs directories

[Russell L. Carter]

On 12/16/14 11:37, John Baldwin wrote:
> On Monday, December 15, 2014 3:59:29 pm Rick Macklem wrote:

[...]

>> What I suspect might cause this is one of two things:
>> 1 - The modify time of the file is now changing at a time the Linux
>>      client doesn't expect, due to changes in ZFS or maybe TOD clock
>>      resolution. (At one time, the TOD clock was only at a resolution
>>      of 1sec, so the client wouldn't see the modify time change often.
>>      I think it is now at a much higher resolution, but would have to
>>      look at the code/test to be sure.)
>
> No, it's still only a second resolution on FreeBSD by default.  You can
> make this precise on the NFS server by setting the vfs.timestamp_precision
> sysctl to 3.  We should probably be using that by default for at least
> server-class systems.
>

Hmm, what's this?  Let's see:

rcarter at feyerabend> uname -a
FreeBSD feyerabend.n1.pinyon.org 10.1-STABLE FreeBSD 10.1-STABLE #1 
r275516+3a52b5f(stable-jhb-em): Sat Dec  6 10:37:16 MST 2014 
toor at feyerabend.n1.pinyon.org:/usr/obj/usr/src/sys/RLCGSV  amd64
rcarter at feyerabend> man -k vfs.timestamp_precision
vfs.timestamp_precision: nothing appropriate
rcarter at feyerabend> sysctl -d vfs.timestamp_precision
vfs.timestamp_precision: File timestamp precision (0: seconds, 1: sec + 
ns accurate to 1/HZ, 2: sec + ns truncated to ms, 3+: sec + ns (max. 
precision))
rcarter at feyerabend> sysctl vfs.timestamp_precision
vfs.timestamp_precision: 0

Ah, that's *VERY* interesting.  I am unfortunately leaving the
physical vicinity of my server farm soon, so not the right time for
experiments.  But I have been whining for some time now about what
looks to be very similar to gerrit.kuehn's symptoms.  I see them on
installworlds via NFS v4.1, on -current or stable/10-trunk.  About 9
out of 10 installs fail trying to rebuild parts of the tree.  I
finally resorted to copying /usr/obj* around and then just mounting
/usr/src via NFS.  ick.  Oh, and also buildworld/buildkernel -j1.  A
pity on a cluster where 8 cores/system are the norm.  But now I have
something sensible to try.  Looking forward to it.

Happy holidays, and cheers!
Russell