Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB

David Hildenbrand
2021-11-24T13:29:14Z

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