On Wed, Apr 14, 2021 at 03:08:19PM +0200, Michal Hocko wrote: > On Wed 17-03-21 11:40:05, Feng Tang wrote: > > From: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > > > Add a helper function which takes care of handling multiple preferred > > nodes. It will be called by future patches that need to handle this, > > specifically VMA based page allocation, and task based page allocation. > > Huge pages don't quite fit the same pattern because they use different > > underlying page allocation functions. This consumes the previous > > interleave policy specific allocation function to make a one stop shop > > for policy based allocation. > > > > With this, MPOL_PREFERRED_MANY's semantic is more like MPOL_PREFERRED > > that it will first try the preferred node/nodes, and fallback to all > > other nodes when first try fails. Thanks to Michal Hocko for suggestions > > on this. > > > > For now, only interleaved policy will be used so there should be no > > functional change yet. However, if bisection points to issues in the > > next few commits, it was likely the fault of this patch. > > I am not sure this is helping much. Let's see in later patches but I > would keep them separate and rather create a dedicated function for the > new policy allocation mode. Thanks for the suggestion, we will rethink the implementations. - Feng > > Similar functionality is offered via policy_node() and > > policy_nodemask(). By themselves however, neither can achieve this > > fallback style of sets of nodes. > > > > [ Feng: for the first try, add NOWARN flag, and skip the direct reclaim > > to speedup allocation in some case ] > > > > Link: https://lore.kernel.org/r/20200630212517.308045-9-ben.widawsky@xxxxxxxxx > > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> > > --- > > mm/mempolicy.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++------------ > > 1 file changed, 52 insertions(+), 13 deletions(-) > > > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > > index d945f29..d21105b 100644 > > --- a/mm/mempolicy.c > > +++ b/mm/mempolicy.c > > @@ -2187,22 +2187,60 @@ bool mempolicy_nodemask_intersects(struct task_struct *tsk, > > return ret; > > } > > > > -/* Allocate a page in interleaved policy. > > - Own path because it needs to do special accounting. */ > > -static struct page *alloc_page_interleave(gfp_t gfp, unsigned order, > > - unsigned nid) > > +/* Handle page allocation for all but interleaved policies */ > > +static struct page *alloc_pages_policy(struct mempolicy *pol, gfp_t gfp, > > + unsigned int order, int preferred_nid) > > { > > struct page *page; > > + gfp_t gfp_mask = gfp; > > > > - page = __alloc_pages(gfp, order, nid); > > - /* skip NUMA_INTERLEAVE_HIT counter update if numa stats is disabled */ > > - if (!static_branch_likely(&vm_numa_stat_key)) > > + if (pol->mode == MPOL_INTERLEAVE) { > > + page = __alloc_pages(gfp, order, preferred_nid); > > + /* skip NUMA_INTERLEAVE_HIT counter update if numa stats is disabled */ > > + if (!static_branch_likely(&vm_numa_stat_key)) > > + return page; > > + if (page && page_to_nid(page) == preferred_nid) { > > + preempt_disable(); > > + __inc_numa_state(page_zone(page), NUMA_INTERLEAVE_HIT); > > + preempt_enable(); > > + } > > return page; > > - if (page && page_to_nid(page) == nid) { > > - preempt_disable(); > > - __inc_numa_state(page_zone(page), NUMA_INTERLEAVE_HIT); > > - preempt_enable(); > > } > > + > > + VM_BUG_ON(preferred_nid != NUMA_NO_NODE); > > + > > + preferred_nid = numa_node_id(); > > + > > + /* > > + * There is a two pass approach implemented here for > > + * MPOL_PREFERRED_MANY. In the first pass we try the preferred nodes > > + * but allow the allocation to fail. The below table explains how > > + * this is achieved. > > + * > > + * | Policy | preferred nid | nodemask | > > + * |-------------------------------|---------------|------------| > > + * | MPOL_DEFAULT | local | NULL | > > + * | MPOL_PREFERRED | best | NULL | > > + * | MPOL_INTERLEAVE | ERR | ERR | > > + * | MPOL_BIND | local | pol->nodes | > > + * | MPOL_PREFERRED_MANY | best | pol->nodes | > > + * | MPOL_PREFERRED_MANY (round 2) | local | NULL | > > + * +-------------------------------+---------------+------------+ > > + */ > > + if (pol->mode == MPOL_PREFERRED_MANY) { > > + gfp_mask |= __GFP_NOWARN; > > + > > + /* Skip direct reclaim, as there will be a second try */ > > + gfp_mask &= ~__GFP_DIRECT_RECLAIM; > > + } > > + > > + page = __alloc_pages_nodemask(gfp_mask, order, > > + policy_node(gfp, pol, preferred_nid), > > + policy_nodemask(gfp, pol)); > > + > > + if (unlikely(!page && pol->mode == MPOL_PREFERRED_MANY)) > > + page = __alloc_pages_nodemask(gfp, order, preferred_nid, NULL); > > + > > return page; > > } > > > > @@ -2244,8 +2282,8 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma, > > unsigned nid; > > > > nid = interleave_nid(pol, vma, addr, PAGE_SHIFT + order); > > + page = alloc_pages_policy(pol, gfp, order, nid); > > mpol_cond_put(pol); > > - page = alloc_page_interleave(gfp, order, nid); > > goto out; > > } > > > > @@ -2329,7 +2367,8 @@ struct page *alloc_pages_current(gfp_t gfp, unsigned order) > > * nor system default_policy > > */ > > if (pol->mode == MPOL_INTERLEAVE) > > - page = alloc_page_interleave(gfp, order, interleave_nodes(pol)); > > + page = alloc_pages_policy(pol, gfp, order, > > + interleave_nodes(pol)); > > else > > page = __alloc_pages_nodemask(gfp, order, > > policy_node(gfp, pol, numa_node_id()), > > -- > > 2.7.4 > > -- > Michal Hocko > SUSE Labs
