Ping RTT clock resolution problem on x86_64

[Joshua Jensen]

Yes!!  Bugzilla is very much a public thing.  Please file it!

On Fri, Oct 22, 2004 at 01:56:29PM -0700, Federico Sacerdoti wrote:
> Not yet, is it open to the public? We have some indication that the 
> "tsc" kernel flag fixes some of the timer problems.
> 
> -Federico
> 
> On Oct 22, 2004, at 7:27 AM, Joshua Jensen wrote:
> 
> >Please say that you have entered this in bugzilla... this is important
> >
> >Joshua
> >
> >
> >
> >On Thu, Oct 14, 2004 at 01:58:57PM -0700, Federico Sacerdoti wrote:
> >>Hello,
> >>
> >>I am a developer from the Rocks project in San Diego. We are noticing 
> >>a
> >>problem with the clock resolution for TCP round trip times that only
> >>emerges on AMD Opteron systems. The bug is characterized as follows:
> >>
> >>The issue is that the clock resolution is only 10ms: ie any rtt value
> >>between 0-10ms is reported as 0.00ms.
> >>
> >>--On Opteron (bug)--
> >>root at www root]# ping google.com
> >>PING google.com (216.239.37.99) 56(84) bytes of data.
> >>64 bytes from 216.239.37.99: icmp_seq=0 ttl=238 time=89.9 ms
> >>64 bytes from 216.239.37.99: icmp_seq=1 ttl=238 time=79.9 ms
> >>64 bytes from 216.239.37.99: icmp_seq=2 ttl=236 time=79.9 ms
> >>
> >>[root at www root]# ping nbc.com
> >>PING nbc.com (63.241.60.70) 56(84) bytes of data.
> >>64 bytes from nbc.com (63.241.60.70): icmp_seq=0 ttl=53 time=0.000 ms
> >>64 bytes from nbc.com (63.241.60.70): icmp_seq=1 ttl=53 time=0.000 ms
> >>
> >>
> >>--On Other systems (normal)--
> >>[root at rocks-43 root]# ping google.com
> >>PING google.com (216.239.57.99) 56(84) bytes of data.
> >>64 bytes from 216.239.57.99: icmp_seq=0 ttl=244 time=11.5 ms
> >>64 bytes from 216.239.57.99: icmp_seq=1 ttl=244 time=11.8 ms
> >>64 bytes from 216.239.57.99: icmp_seq=2 ttl=244 time=11.5 ms
> >>64 bytes from 216.239.57.99: icmp_seq=3 ttl=244 time=11.7 ms
> >>
> >>[root at rocks-43 root]# ping nbc.com
> >>PING nbc.com (63.241.60.70) 56(84) bytes of data.
> >>64 bytes from nbc.com (63.241.60.70): icmp_seq=0 ttl=53 time=7.41 ms
> >>64 bytes from nbc.com (63.241.60.70): icmp_seq=1 ttl=53 time=7.32 ms
> >>64 bytes from nbc.com (63.241.60.70): icmp_seq=2 ttl=53 time=7.39 ms
> >>64 bytes from nbc.com (63.241.60.70): icmp_seq=3 ttl=53 time=7.33 ms
> >>
> >>
> >>This behavior happens for several different types of ethernet cards on
> >>opterons, and is not observed on either Pentium or Nocona systems.
> >>
> >>Has anyone noticed this before? Our kernel version is:
> >>
> >>(Nocona)
> >>Linux rocks-43.sdsc.edu 2.4.21-20.EL #1 SMP Fri Oct 1 09:12:23 PDT 
> >>2004
> >>x86_64 x86_64 x86_64 GNU/Linux
> >>
> >>(Opteron)
> >>Linux www.rocksclusters.org 2.4.21-20.ELsmp #1 SMP Sat Sep 18 18:28:16
> >>PDT 2004 x86_64 x86_64 x86_64 GNU/Linux
> >>
> >>Thank you,
> >>Federico
> >>
> >>Rocks Cluster Group, San Diego Supercomputer Center, CA
> >>
> >>-- 
> >>amd64-list mailing list
> >>amd64-list at redhat.com
> >>https://www.redhat.com/mailman/listinfo/amd64-list
> >
> >-- 
> >Joshua Jensen
> >joshua at iwsp.com
> >"If God didn't want us to eat animals, why did he make them out of 
> >meat?"
> >
> >-- 
> >amd64-list mailing list
> >amd64-list at redhat.com
> >https://www.redhat.com/mailman/listinfo/amd64-list
> >
> Federico
> 
> Rocks Cluster Group, San Diego Supercomputer Center, CA

-- 
Joshua Jensen
joshua at iwsp.com
"If God didn't want us to eat animals, why did he make them out of meat?"