Ping RTT clock resolution problem on x86_64

[Federico Sacerdoti]

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