Re: Question regarding SLAB corruption

[Roland Dreier <rdreier@cisco.com>]

 > Great! With this "fix", it turns on interface ib0. Many thanks to all!

in domU?  That is cool.

 > Anyway, is this fix limiting some features, latencies or throughput?

It is getting rid of the FMR feature entirely and also affecting
memory registration speed.  Although going through an swiotlb memcpy
may eliminate the memory registration speed advantage.  Anyway things
are quite useful without the direct write to the MTT -- I think Lustre
may be the only thing that *has* to have FMRs, and the memory
registration optimization is not that important; we didn't have it for
quite a while and it wasn't *that* big a deal.

Anyway I think the real fix is to switch to dma_sync_single_range in
mthca along with Keir's fixes to swiotlb.

Although I'm a little confused about the earlier parts of the story.
Why was it necessary to force the use of swiotlb?  Shouldn't things
work by default?

And is there any more intelligent way to give big chunks of system
memory to a PCI device for exclusive use?

 - R.