[ntp:questions] NTP vs RADclock?

Rick Jones rick.jones2 at hp.com
Fri Jun 8 23:25:00 UTC 2012


unruh <unruh at invalid.ca> wrote:
> I am sure that it started when we switched from 100Mb technology to
> Gb technology, yes. Other places to look for the problem would be
> appreciated.

I would suggest then trying disabling of the interrupt coalescing via
ethtool on the 1GbE NIC of your server and a few select clients and
see what that does.  If things start to look cleaner then you know it
is an implementation-specific detail of one or more GbE NICs.

If it is possible to connect a client "back-to-back" to your server at
the same time (via a second port) - still with interrupt coalescing
disabled at both ends that would be an excellent addition.  That will
help evaluate the switch.

I trust there were no OS changes when going from 100BT to GbE?  Though
even if not, there is still the prospect of the drivers for the 100BT
cards not doing what linux calls "napi" and the drivers for the GbE
cards doing it, which may introduce some timing changes.

> So yes, I think it is the Gb technology that is causing trouble. 

I split what may seem a hair between Gb technology being the IEEE
specification and Gb implementation being what specific NIC vendors
do.  So, to me, interrupt coalescing is implementation not technology.  

rick jones
-- 
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