Re: Ping RTT clock resolution problem on x86_64

[Federico Sacerdoti <fds@xxxxxxxx>]

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@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@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@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@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@xxxxxxxxxx
> > https://www.redhat.com/mailman/listinfo/amd64-list
>
> --
> Joshua Jensen
> joshua@xxxxxxxx
> "If God didn't want us to eat animals, why did he make them out of 
> meat?"
>
> --
>
> amd64-list@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/amd64-list
Federico

Rocks Cluster Group, San Diego Supercomputer Center, CA

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