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

From: Michael R. Hines
Date: Tue Apr 09 2013 - 13:56:32 EST

On 04/09/2013 12:39 PM, Michael S. Tsirkin wrote:
On Fri, Apr 05, 2013 at 04:54:39PM -0400, Michael R. Hines wrote:
To be more specific, here's what I did:

1. apply kernel module patch - re-insert module
1. QEMU does: ibv_reg_mr(........IBV_ACCESS_GIFT | IBV_ACCESS_REMOTE_READ)
2. Start the RDMA migration
3. Migration completes without any errors

This test does *not* work with a cgroup swap limit, however. The
process gets killed. (Both with and without GIFT)

- Michael
Try to attach a debugger and see where it is when it gets killed?

It's killed by cgroups - not a CPU exception.

The same test works fine using TCP migration with cgroups - everything is fine there.

The memory that RDMA attempted to register hits some kind of cgroups policy
which results in a kernel message saying that the cgroup swap limit was hit
and then it goes ahead and kills the process altogether.

It's not a QEMU problem - it seems to be a kernel bug.

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