lkml.org 
[lkml]   [2020]   [Nov]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/3] mm,thp,shm: limit gfp mask to no more than specified
From
Date
On Mon, 2020-11-30 at 11:00 +0100, Michal Hocko wrote:
> On Fri 27-11-20 14:03:39, Rik van Riel wrote:
> > On Fri, 2020-11-27 at 08:52 +0100, Michal Hocko wrote:
> > > On Thu 26-11-20 13:04:14, Rik van Riel wrote:
> > > > I would be more than happy to implement things differently,
> > > > but I am not sure what alternative you are suggesting.
> > >
> > > Simply do not alter gfp flags? Or warn in some cases of a serious
> > > mismatch.
> > > E.g. GFP_ZONEMASK mismatch because there are already GFP_KERNEL
> > > users
> > > of
> > > shmem.
> >
> > Not altering the gfp flags is not really an option,
> > because that would leads to attempting to allocate THPs
> > with GFP_HIGHUSER, which is what is used to allocate
> > regular tmpfs pages.
>
> Right but that is a completely different reason to alter the mask and
> it
> would be really great to know whether this is a theoretical concern
> or
> those users simply do not ever use THPs. Btw. should they be using
> THPs
> even if they opt themselves into GFP_KERNEL restriction?

I suppose disabling THPs completely if the gfp_mask
passed to shmem_getpage_gfp() is not GFP_HIGHUSER
is another option.

That seems like it might come with its own pitfalls,
though, both functionality wise and maintenance wise.

Does anyone have
strong feelings between "limit gfp_mask"
and "disable THP for !GFP_HIGHUSER"?

--
All Rights Reversed.
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2020-11-30 15:43    [W:0.064 / U:0.712 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site