[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: High-Precision NFS Timestamps
From: |
Eric Blake |
Subject: |
Re: High-Precision NFS Timestamps |
Date: |
Wed, 12 Jan 2011 15:30:07 -0700 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Lightning/1.0b3pre Mnenhy/0.8.3 Thunderbird/3.1.7 |
[adding bug-make, replies can drop automake]
On 01/12/2011 03:08 PM, Eric Reischer wrote:
> I recently upgraded our NFS fileserver to an ext4 filesystem, and since
> then we've been having clock skew warnings from make (3.81). Because
> the ext3 filesystem that was previously running on the NFS server didn't
> support high-precision timestamps, we didn't have clock skew warnings
> because an hourly cron job kept the clocks in relatively close sync.
> However, since ext4 does support sub-second timestamps, we're getting
> warnings about clock skews on the order of a few milliseconds. I tried
> adding our target objects to the .LOW_RESOLUTION_TIME target, however
> now we're getting a warning about
>
> make: *** Warning: .LOW_RESOLUTION_TIME file .lib_deps has a high
> resolution time stamp
> make: warning: Clock skew detected. Your build may be incomplete.
>
> Since asking to have system clocks of NFS clients and servers synced to
> sub-millisecond precision is a bit excessive, is there a way (or feature
> request: could there be a way) to set the threshold for clock skews
> either via a runtime Makefile directive, or an environment variable? I
> can't see any other way to eliminate these warnings without reverting
> back to ext3 (which isn't happening). If it's a hard-coded value, there
> should be at least a little room for slop in there (~5 milliseconds?)
> due to network lag, etc. Even on a point-to-point network, there's
> going to be one-way transit times of a millisecond or two.
This is more likely a make issue than an automake issue.
That said, NFS timestamps are indeed a source of pain, and gnulib has
recently put in quite a bit of work dealing with timestamp skew across
NFS (including code to ignore relatively close timestamps, rather than
insist that sub-millisecond differences represent skew); some of that
may be worth incorporating into the make code base if it isn't there
already.
--
Eric Blake address@hidden +1-801-349-2682
Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: High-Precision NFS Timestamps,
Eric Blake <=