Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-13 Thread Brett Glass
Thank you! Since it's tunable at runtime I just tested it, and -- sure enough -- no negative ping times. Ironically, it was the kernel that selected the ACPI timer, scoring it higher than the timestamp counter as a clock source. Perhaps code should be added to ensure that the timer is not chosen

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-13 Thread Brett Glass
At 09:16 AM 9/13/2011, Dan Nelson wrote: It doesn't roll over in less than a second; it rolls over in 16777215 / 3579545 = 4.6 seconds. Your negative time delta problem isn't due to rollover. If that's indeed the case, the kernel must be doing the math wrong. I wonder how many other systems

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-13 Thread Chuck Swiger
[ ...combining two emails... ] On Sep 13, 2011, at 9:49 AM, Brett Glass wrote: If that's indeed the case, the kernel must be doing the math wrong. While there have undoubtedly have been kernel bugs with timekeeping (and there may be more still present), it's not uncommon for hardware issues to

Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread Brett Glass
Here's a puzzler. I just put FreeBSD 8.1 up on an old (but good) 500 MHz Celeron with half a gig of RAM. Interfaces are classic xl (3Com) and dc (DEC tulip). Works quite nicely except for one quirk: ping times that ought to be positive (no more than 200 ms worst case) are coming out

RE: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread Brett Glass
More information regarding the odd behavior I'm seeing. Turns out that packets do not even need to leave the machine for it to report large negative ping times, on the order of more than half a second. (See below.) Clearly something is odd about timekeeping in this system (SiS motherboard

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread Chuck Swiger
On Sep 12, 2011, at 4:50 PM, Brett Glass wrote: What's more, it appears that the negative ping times being shown for pings of localhost are off by about -687 ms, consistently. Any ideas? Your system's timekeeping appears to be busted. Are you running ntpd with tinker step 0.0 or some

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread b. f.
I just put FreeBSD 8.1 up on an old (but good) 500 MHz Celeron with half a gig of RAM. Interfaces are classic xl (3Com) and dc (DEC tulip). Works quite nicely except for one quirk: ping times that ought to be positive (no more than 200 ms worst case) are coming out negative! Can't figure out

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread Brett Glass
At 06:15 PM 9/12/2011, Chuck Swiger wrote: Your system's timekeeping appears to be busted. Are you running ntpd with tinker step 0.0 or some home-grown mechanism which might be forcibly stepping the clock rather than skewing it, by any chance? Nothing like that. Anyway, the output of:

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread Brett Glass
At 06:54 PM 9/12/2011, b. f. wrote: If you are just upgrading now, why not use 9 BETA? Production machine. Also, whenever we create a new production box, we normally pick the release (not beta; we need to be able to do binary upgrades and this is only supported from one release to another)

Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

2011-09-12 Thread Adam Vande More
On Mon, Sep 12, 2011 at 10:30 PM, Brett Glass br...@lariat.net wrote: At 06:15 PM 9/12/2011, Chuck Swiger wrote: sysctl -a kern.timecounter No docs on how to do this. Is this done by, for example, setting kern.timecounter.hardware=TSC in loader.conf? it's a runtime tunable so