On Mon 12-07-21 16:09:30, Feng Tang wrote: > The semantics of MPOL_PREFERRED_MANY is similar to MPOL_PREFERRED, > that it will first try to allocate memory from the preferred node(s), > and fallback to all nodes in system when first try fails. > > Add a dedicated function for it just like 'interleave' policy. > > Link: https://lore.kernel.org/r/20200630212517.308045-9-ben.widawsky@xxxxxxxxx > Suggested-by: Michal Hocko <mhocko@xxxxxxxx> > Co-developed-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> It would be better to squash this together with the actual user of the function added by the next patch. > --- > mm/mempolicy.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 17b5800b7dcc..d17bf018efcc 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -2153,6 +2153,25 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order, > return page; > } > > +static struct page *alloc_page_preferred_many(gfp_t gfp, unsigned int order, > + struct mempolicy *pol) We likely want a node parameter to know which one we want to start with for locality. Callers should use policy_node for that. > +{ > + struct page *page; > + > + /* > + * This is a two pass approach. The first pass will only try the > + * preferred nodes but skip the direct reclaim and allow the > + * allocation to fail, while the second pass will try all the > + * nodes in system. > + */ > + page = __alloc_pages(((gfp | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM), > + order, first_node(pol->nodes), &pol->nodes); Although most users will likely have some form of GFP_*USER* here and clearing __GFP_DIRECT_RECLAIM will put all other reclaim modifiers out of game I think it would be better to explicitly disable some of them to prevent from surprises. E.g. any potential __GFP_NOFAIL would be more than surprising here. We do not have any (hopefully) but this should be pretty cheap to exclude as we already have to modify already. preferred_gfp = gfp | __GFP_NOWARN; preferred_gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL) > + if (!page) > + page = __alloc_pages(gfp, order, numa_node_id(), NULL); > + > + return page; > +} > + > /** > * alloc_pages_vma - Allocate a page for a VMA. > * @gfp: GFP flags. > -- > 2.7.4 -- Michal Hocko SUSE Labs
