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. > 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
