On 12/16/14 20:39, Russell L. Carter wrote:
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@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
t...@feyerabend.n1.pinyon.org:/usr/obj/usr/src/sys/RLCGSV amd64
rcarter@feyerabend> man -k vfs.timestamp_precision
vfs.timestamp_precision: nothing appropriate
rcarter@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@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.
After figuring out a way to test this reversibly, I tried the following:
server & client vfs.timestamp_precision=3, make -j12 buildworld/kernel,
and make installworld -j1 on the client => fail, in /usr/src/sys/boot
server & client vfs.timestamp_precision=0, make -j1 build/install,
succeeds.
Worth a shot anyway...
Cheers,
Russell
Happy holidays, and cheers!
Russell
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