linux-kernel - Re: [RFC PATCH 4/4] hugetlb: add support for preferred node to alloc_huge_page

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Date:   Mon, 12 Jun 2017 14:20:35 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Xishi Qiu <qiuxishi@...wei.com>,
        zhong jiang <zhongjiang@...wei.com>,
        Joonsoo Kim <js1304@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 4/4] hugetlb: add support for preferred node to
 alloc_huge_page_nodemask

On Mon 12-06-17 13:53:51, Vlastimil Babka wrote:
> On 06/12/2017 11:06 AM, Michal Hocko wrote:
[...]
> > -/* Movability of hugepages depends on migration support. */
> > -static inline gfp_t htlb_alloc_mask(struct hstate *h)
> > +static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
> >  {
> > -	if (hugepages_treat_as_movable || hugepage_migration_supported(h))
> > -		return GFP_HIGHUSER_MOVABLE;
> > -	else
> > -		return GFP_HIGHUSER;
> > +	if (nid != NUMA_NO_NODE)
> > +		return dequeue_huge_page_node_exact(h, nid);
> > +
> > +	return dequeue_huge_page_nodemask(h, nid, NULL);
> 
> This with nid == NUMA_NO_NODE will break at node_zonelist(nid,
> gfp_mask); in dequeue_huge_page_nodemask(). I guess just use the local
> node as preferred.

You are right. Anyway I have a patch to remove this helper altogether.

> > -retry_cpuset:
> > -	cpuset_mems_cookie = read_mems_allowed_begin();
> > -	gfp_mask = htlb_alloc_mask(h);
> > -	nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
> > -	zonelist = node_zonelist(nid, gfp_mask);
> > -
> > -	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> > -						MAX_NR_ZONES - 1, nodemask) {
> > -		if (cpuset_zone_allowed(zone, gfp_mask)) {
> > -			page = dequeue_huge_page_node(h, zone_to_nid(zone));
> > -			if (page) {
> > -				if (avoid_reserve)
> > -					break;
> > -				if (!vma_has_reserves(vma, chg))
> > -					break;
> > -
> > -				SetPagePrivate(page);
> > -				h->resv_huge_pages--;
> > -				break;
> > -			}
> > -		}
> > +	nid = huge_node(vma, address, htlb_alloc_mask(h), &mpol, &nodemask);
> > +	page = dequeue_huge_page_nodemask(h, nid, nodemask);
> > +	if (page && !(avoid_reserve || (!vma_has_reserves(vma, chg)))) {
> 
> Ugh that's hard to parse.
> What about: if (page && !avoid_reserve && vma_has_reserves(...)) ?

Yeah, I have just translated the two breaks into a single condition
without scratching my head to much. If you think that this face of De Morgan
is nicer I can use it.
-- 
Michal Hocko
SUSE Labs