Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB

Jason Gunthorpe
2021-11-24T14:34:03Z

On Wed, Nov 24, 2021 at 02:25:09PM +0100, David Hildenbrand wrote:
> 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 :)

?? Where is that done in GUP?

Jason