Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag

Michal Hocko
2020-08-11T10:28:23Z

On Tue 11-08-20 11:42:51, Uladzislau Rezki wrote:
> On Tue, Aug 11, 2020 at 11:37:13AM +0200, Uladzislau Rezki wrote:
> > On Tue, Aug 11, 2020 at 10:19:17AM +0200, Michal Hocko wrote:
[...]
> > > Anyway, if the zone->lock is not a good fit for raw_spin_lock then the
> > > only way I can see forward is to detect real (RT) atomic contexts and
> > > bail out early before taking the lock in the allocator for NOWAIT/ATOMIC
> > > requests.
> > >
> This is similar what i have done with mm: Add __GFP_NO_LOCKS flag. I just
> did it for order-0 pages(other paths are impossible) and made it common for
> any kernel.
>
> Because when you say "bail out early" i suspect that we would like to check
> the per-cpu-list cache.

Bail out early means to do as much as possible until a raw non-compliant
lock has to be taken.

--
Michal Hocko
SUSE Labs