[ofa-general] [PATCH] IB/mlx4: Use pgprot_writecombine() for BlueFlame pages

[Or Gerlitz]

Roland Dreier wrote:
> So the OFED WC patch is work 2.3usec??  Or did you mean 1.2usec vs. 1.5usec?

see detailed results below, I used ib_rdma_lat -n 50000 and ignored the maximal
result as it seems to be very different between runs over the same configuration- I think we can do well without taking it into account as the best and typical results are very close under all configs. 

Don't know if its good or bad... but the news are that I can't reproduce the 3.5us result any more. Without any patches, with/without CONFIG_X86_PAT gives the same results... and both your patch and ofed's take the latency down by 20% 

I'll send you my .config where the difference between the 1st vs the 2nd,3rd 4th runs is CONFIG_X86_PAT - the setup is made of 2 super-micro nodes, pcie gen2, connectx ddr fw 2.6 and Linux 2.6.29 ...

> In any case it seems my patch is not working on your system.  Do you
> have CONFIG_X86_PAT set in your kernel .config?

2.6.29 without CONFIG_X86_PAT 
Latency typical: 1.43087 usec
Latency best   : 1.41287 usec

2.6.29 + CONFIG_X86_PAT 
Latency typical: 1.43245 usec
Latency best   : 1.41295 usec

2.6.29 + CONFIG_X86_PAT + your patch
Latency typical: 1.14896 usec
Latency best   : 1.12646 usec

2.6.29 + CONFIG_X86_PAT + ofed's patch
Latency typical: 1.14746 usec
Latency best   : 1.12646 usec