Hello,
We have been testing latency and bandwidth using our proprietary MPI link checker tool (http://www.microway.com/mpilinkchecker.html) and have found that the latency increased from ~25ms to ~45ms going from 2.6.11 to 2.6.12. 2.6.13 has the same result. We also tried the latest bcm5700 from broadcom (8.2.18) and got the same ~45ms latencies. This was tried on several different opteron and em64t motherboards.
We see 20-25ms latencies with the e1000 driver (with some module options) on all 3 kernel versions. For those interested, the e1000 options used are:
InterruptThrottleRate=0 RxIntDelay=0 TxIntDelay=0 RxAbsIntDelay=0 TxAbsIntDelay=0
Digging through source, it seems that a new locking mechanism for tg3 was put in place in 2.6.12. Is this the likely cause? What can we do to restore our lower latency?