On Wed, Jul 28, 2021 at 02:42:26PM +0200, Michal Hocko wrote: > 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. Ok, will do > > --- > > 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. Yes, locality should be considered, something like this? int pnid, lnid = numa_node_id(); if (is_nodeset(lnid, &pol->nodes)) pnid = local_nid; else pnid = first_node(pol->nodes); page = __alloc_pages(((gfp | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM), order, pnid, &pol->nodes); if (!page) page = __alloc_pages(gfp, order, lnid, NULL); return page; > > +{ > > + 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) OK, will add. Thanks, Feng > > > + 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
