On Fri 26-06-20 14:02:49, Joonsoo Kim wrote:
> 2020년 6월 25일 (목) 오후 9:05, Michal Hocko <mhocko@xxxxxxxxxx>님이 작성:
> >
> > On Tue 23-06-20 15:13:45, Joonsoo Kim wrote:
[...]
> > > -struct page *new_page_nodemask(struct page *page,
> > > - int preferred_nid, nodemask_t *nodemask)
> > > +struct page *alloc_migration_target(struct page *page, unsigned long private)
> > > {
> > > - gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL;
> > > + struct migration_target_control *mtc;
> > > + gfp_t gfp_mask;
> > > unsigned int order = 0;
> > > struct page *new_page = NULL;
> > > + int zidx;
> > > +
> > > + mtc = (struct migration_target_control *)private;
> > > + gfp_mask = mtc->gfp_mask;
> > >
> > > if (PageHuge(page)) {
> > > return alloc_huge_page_nodemask(
> > > - page_hstate(compound_head(page)),
> > > - preferred_nid, nodemask, 0, false);
> > > + page_hstate(compound_head(page)), mtc->nid,
> > > + mtc->nmask, gfp_mask, false);
> > > }
> > >
> > > if (PageTransHuge(page)) {
> > > + gfp_mask &= ~__GFP_RECLAIM;
> >
> > What's up with this gfp_mask modification?
>
> THP page allocation uses a standard gfp masks, GFP_TRANSHUGE_LIGHT and
> GFP_TRANHUGE. __GFP_RECLAIM flags is a big part of this standard mask design.
> So, I clear it here so as not to disrupt the THP gfp mask.
Why this wasn't really needed before? I guess I must be missing
something here. This patch should be mostly mechanical convergence of
existing migration callbacks but this change adds a new behavior AFAICS.
It would effectively drop __GFP_RETRY_MAYFAIL and __GFP_KSWAPD_RECLAIM
from the mask so the allocation would "lighter". If that is your
intention then this should be a separate patch with an explanation
rather than hiding it into this patch.
--
Michal Hocko
SUSE Labs
