Re: [LSF/MM/BPF TOPIC] Discussion: Targeted memory allocation via debugfs

["David Hildenbrand (Arm)" <david@kernel.org>]

>> So maybe you really want a debug mechanism to migrate a (movable) user
>> space page into a CMA area?
>>
> One intent of this driver is to debug CMA issues (pinned MOVABLE pages). This
> The driver will allow easy reproduction of the case you just
> mentioned. For example,
> I will allocate most of the MOVABLE pages and then trigger a CMA
> allocation, that might trigger a migration.
> 
> However, the driver's main goal is to put the system into low-memory conditions.
> so we can reproduce OOO, kswad, lmkd issues seeing in the devices.

(Late reply ...)

But there are other ways to trigger low-memory conditions, no?

So I think the real missing piece you are looking for is getting a movable
userspace page allocated on CMA memory, to then try allocating from CMA to see
if migration works.

And you can do a bunch of things to make CMA's life has hard as possible.
O_DIRECT the userspace page, trigger low-memory conditions etc.

-- 
Cheers,

David