Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB

From: Andrew Morton
Date: Thu Nov 18 2021 - 16:58:55 EST

On Wed, 17 Nov 2021 16:17:26 -0700 Jens Axboe <axboe@xxxxxxxxx> wrote:

> On 11/17/21 3:26 PM, Johannes Weiner wrote:
> >> Link:
> >> Signed-off-by: Drew DeVault <sir@xxxxxxxxx>
> >> Acked-by: Jens Axboe <axboe@xxxxxxxxx>
> >> Acked-by: Cyril Hrubis <chrubis@xxxxxxx>
> >> Cc: Pavel Begunkov <asml.silence@xxxxxxxxx>
> >> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> >
> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> >
> > As per above, I think basing it off of RAM size would be better, but
> > this increase is overdue given all the new users beyond mlock(), and
> > 8M is much better than the current value.
> That's basically my reasoning too. Let's just get something going that
> will at least unblock some valid use cases, and not get bogged down with
> aiming for perfection. The latter can happen in parallel, but it should
> not hold it up imho.

Nobody's aiming for perfection. We're discussing aiming for "better".

What we should have done on day one was to set the default MLOCK_LIMIT
to zero bytes. Then everyone would have infrastructure to tune it from
userspace and we wouldn't ever have this discussion.