Re: [PATCHv2] rdma: add a new IB_ACCESS_GIFT flag

From: Michael S. Tsirkin
Date: Tue Apr 09 2013 - 16:17:49 EST

On Fri, Apr 05, 2013 at 01:43:49PM -0700, Roland Dreier wrote:
> On Fri, Apr 5, 2013 at 1:17 PM, Michael R. Hines
> <mrhines@xxxxxxxxxxxxxxxxxx> wrote:
> > I also removed the IBV_*_WRITE flags on the sender-side and activated
> > cgroups with the "memory.memsw.limit_in_bytes" activated and the migration
> > with RDMA also succeeded without any problems (both with *and* without GIFT
> > also worked).
> Not sure I'm interpreting this correctly. Are you saying that things
> worked without actually setting the GIFT flag? In which case why are
> we adding this flag?
> - R.

We are adding the flag to reduce memory when there's lots of COW pages.
There's no guarantee there will be COW pages so I expect things to work
both with and without breaking COW, just using much more memory when we
break COW.

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