Re: [LSF/MM/BPF TOPIC] BoF VM live migration over CXL memory​

["Huang, Ying" <ying.huang@intel.com>]

Dragan Stancevic <dragan@stancevic.com> writes:

> On 4/11/23 01:37, Huang, Ying wrote:
>> Gregory Price <gregory.price@memverge.com> writes:
>> [snip]
>> 
>>> 2. During the migration process, the memory needs to be forced not to be
>>>     migrated to another node by other means (tiering software, swap,
>>>     etc).  The obvious way of doing this would be to migrate and
>>>     temporarily pin the page... but going back to problem #1 we see that
>>>     ZONE_MOVABLE and Pinning are mutually exclusive.  So that's
>>>     troublesome.
>> Can we use memory policy (cpusets, mbind(), set_mempolicy(), etc.)
>> to
>> avoid move pages out of CXL.mem node?  Now, there are gaps in tiering,
>> but I think it is fixable.
>
>
> Hmmm, I don't know about cpusets. For mbind, are you thinking
> something along the lines of MPOL_MF_MOVE_ALL? I guess it does have
> that deterministic placement, but this would have to be called from
> the process itself. Unlike migrate_pages which takes a pid.

You can still use migrate_pages(2).  But after that, if you want to
prevent the pages to be migrated out of CXL.mem, you can use some kind
of memory policy, such as cpusets, mbind(), set_mempolicy().

Best Regards,
Huang, Ying

> Same for set_mempolicy, right?
>
> I mean I guess, if some of this needs to be added into qemu it's not
> the end of the word...
>
>
>> Best Regards,
>> Huang, Ying
>> [snip]
>>