# Re: \[PATCH\] Increase default MLOCK\_LIMIT to 8 MiB

- From: David Hildenbrand \<hidden\>
- Date: 2021-11-24 13:29:22 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/11/1584857
- Thread: https://ratatoskr.run/linux-api/2021/10/1556573/t.md

```text
On 24.11.21 14:23, Jason Gunthorpe wrote:
> On Wed, Nov 24, 2021 at 09:57:32AM +0100, David Hildenbrand wrote:
> 
>> Unfortunately it will only be a band aid AFAIU. I can rewrite my
>> reproducer fairly easily to pin the whole 2M range first, pin a second
>> time only a single page, and then unpin the 2M range, resulting in the
>> very same way to block THP. (I can block some THP less because I always
>> need the possibility to memlock 2M first, though).
> 
> Oh!
> 
> The issue is GUP always pins an entire compound, no matter how little
> the user requests.

That's a different issue. I make sure to split the compound page before
pinning anything :)

-- 
Thanks,

David / dhildenb

```