Re: [myrinet] [Q] latency toggle problem

From the keyboard of Moon-Sang Lee:
  > 
  > 
  > Hello, there
  > I'm testing my own MCP on myrinet which use Lanai 7.2.
  > And I found that the latency toggles whenever I reload my MCP and kernel 
  > driver. When I first load my MCP, it seems perform well and shows X latency.
  > And then  if I reload my MCP after I test the correctness of my MCP, it also 
  > seems perform well but shows Y latency.(where X > Y)
  > And if I reload my MCP again, it shows Z latency.(where {X,Z} > Y)
  > Ok. reload again. then it shows it shows A latency.(where {X,Z} > {Y,A})
  > And this toggle of latency continues whenever I load my MCP.
  > Is there anybody who experienced similar situations? 
  > Thanks for reading and any comment will be welcome. 

We have seen something similar, but it was the DMA bandwidth across
the PCI bus that fluctuated quite a bit. We use our own drivers
and MCPs and during the MCP load we run some PCI bus integrity
and performance tests. Every time we loaded an MCP, we would get
different bandwidth numbers. I think that was on LANai 4.x and
9.x on 500MHz DEC Alpha Miatas. I haven't had time to go back and
investigate this more thoroughly.

I just thought I throw this little bit of information in to encourage
other people to report anything strange they might have seen. Maybe
this needs further investigation.

Rolf



+++-+--+----+-------+------------+--------------------+------------------------
Rolf Riesen                              Email: [email protected] [email protected]
Scalable Computing Systems               [email protected]
Sandia National Laboratories             WWW:   http://www.cs.sandia.gov/~rolf
Org. 9223,  MS 1110                      Work:  (505) 845-7363
Albuquerque, NM  87185-1110              Fax:   (505) 845-7442