[openib-general][patch review] srp: fmr implementation,

[Roland Dreier]

    Vu> I don't have a good test to measure performance; however, I
    Vu> ran multiple dd streams on raw devices (no filesystem or
    Vu> buffer cache involved) to measure the impact of using
    Vu> FMRs. With Mellanox srp target referenced implementation SW +
    Vu> 14 SATA drives + PCI-E lion cub, I hit 850 MB/s with FMRs and
    Vu> 710 MB/s without it.

Hmm, I'm not sure whether dd is a good test.  I'd be more interested
to know if typical filesystem I/O generates requests that are
mergeable via FMRs.

    Vu> Do you have a good test to measure performance?

No, I don't.  That's why I ask.

    Vu> Please locally apply the patch, measure the performance impact
    Vu> and post any numbers if possible with your setup

Yes, I need to do that, and also add some instrumentation to see how
often FMRs are used on different workloads.

 - R.