Re: [ofa-general] Re: Demand paging for memory regions

Steve Wise
2008-02-14T16:24:19Z

Robin Holt wrote:
> On Thu, Feb 14, 2008 at 09:09:08AM -0600, Steve Wise wrote:
>> Note that for T3, this involves suspending _all_ rdma connections that are
>> in the same PD as the MR being remapped. This is because the driver
>> doesn't know who the application advertised the rkey/stag to. So without
>
> Is there a reason the driver can not track these.
>

Because advertising of a MR (ie telling the peer about your rkey/stag,
offset and length) is application-specific and can be done out of band,
or in band as simple SEND/RECV payload. Either way, the driver has no
way of tracking this because the protocol used is application-specific.

>> Point being, it will stop probably all connections that an application is
>> using (assuming the application uses a single PD).
>
> It seems like the need to not stop all would be a compelling enough reason
> to modify the driver to track which processes have received the rkey/stag.
>

Yes, _if_ the driver could track this.

And _if_ the rdma API and paradigm was such that the kernel/driver could
keep track, then remote revokations of MR tags could be supported.

Stevo