Hi Mel,
On 02/06/2013 05:56 PM, Mel Gorman wrote:
There is the possibility that callbacks could be introduced for
migrate_unpin() and migrate_pin() that takes a list of PFN pairs
(old,new). The unpin callback should release the old PFNs and barrier
against any operations until the migrate_pfn() callback is called with
the updated pfns to be repinned. Again it would fully depend on subsystems
implementing it properly.
The callback interface would be more robust but puts a lot more work on
the driver side where your milage will vary.
I'm very interested in the "callback" way you said.
For memory hot-remove case, the aio pages are pined in memory and making
the pages cannot be offlined, furthermore, the pages cannot be removed.
IIUC, you mean implement migrate_unpin() and migrate_pin() callbacks in aio
subsystem, and call them when hot-remove code tries to offline pages,
right ?
If so, I'm wondering where should we put this callback pointers ?
In struct page ?
It has been a long time since this topic was discussed. But to solve this
problem cleanly for hotplug guys and CMA guys, please give some more
comments.
Thanks. :)
To guarantee CMA can migrate pages pinned by drivers I think you need
migrate-related callsbacks to unpin, barrier the driver until migration
completes and repin.
I do not know, or at least have no heard, of anyone working on such a
scheme.
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