Re: [PATCH RFC] mm: allow __GFP_NOFAIL allocation up to BLK_MAX_BLOCK_SIZE to support LBS

[Baokun Li <libaokun@huaweicloud.com>]

On 2025-11-05 00:43, Michal Hocko wrote:
> On Tue 04-11-25 13:57:35, Vlastimil Babka wrote:
>> On 11/4/25 1:50 PM, Michal Hocko wrote:
>>> On Tue 04-11-25 13:32:52, Vlastimil Babka wrote:
>>>> OK, it might not create an order-3 page immediately. But I'd expect it
>>>> allows compaction to make progress thanks to making more free memory
>>>> available? We do retry reclaim/compaction after OOM killing one process,
>>>> and don't just kill until we succeed allocating, right?
>>> Yes we do go through the reclaim/compaction cycle. Do you think this
>>> warning is overzealous? Th idea is that a flood of OOMs could be easier
>> I think it's too odd to warn for a specific order and not that or higher
>> orders. We would risk someone would make the allocation order-4 instead
>> of order-3 just to avoid it.
> higher orders simply avoid OOM killer so it is effectivelly retry loop
> around the allocator. Order-3 is a bit odd and that is what the warning
> is trying to tell. But fair enough let's just drop the existing warning
> and see how it goes.
>
Okay, since most people agree that we should first remove the current
warning and then observe what happens before making further decisions,
I will send a patch that directly deletes the warning.

Afterwards, depending on the situation once the warning is removed,
we can consider adding some special handling in other places if needed.

Thanks to everyone for the discussion and suggestions! 


Cheers,
Baokun