Re: [Lsf-pc] [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM)

[David Hildenbrand (Arm)]

On 6/15/26 17:27, Vlastimil Babka (SUSE) wrote:
> On 6/15/26 17:18, David Hildenbrand (Arm) wrote:
>> On 6/15/26 16:38, Vlastimil Babka (SUSE) wrote:
>>>
>>> I think the memalloc approach is dangerous due to unexpected nesting. There
>>> might be nested page allocations in page allocation itself (due to some
>>> debugging option). But also interrupts do not change what "current" points
>>> to. Suddenly those could start requesting folios and/or private nodes and be
>>> surprised, I'm afraid.
>>
>> Yeah, we'd need some way to distinguish the main allocation from these other
>> (nested) allocations.
> 
> That goes against the very principle of scopes. And I don't see how, except
> via a ... flag to the main allocation :D

Unless we teach the handful of debug callpaths to set a custom context. Have
some memalloc_context_save/restore.

I'd assume that the number of such nested allocations we can trigger from the
buddy (through some callbacks like kasan and such) should be rather limited.

I also wonder for a second whether we could use of the _noprof vs. !_noprof
mechanism.

Essentially, calling a !_noprof variant ("external allocation interface") could
mean "save/restore folio allocation". Just a thought.

-- 
Cheers,

David