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Message-ID: <cb18b8ad-af25-b269-3808-5a7452ee2d60@suse.cz>
Date: Mon, 12 Jun 2017 13:53:51 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Michal Hocko <mhocko@...nel.org>
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 06/12/2017 11:06 AM, Michal Hocko wrote:
> On Thu 08-06-17 10:38:06, Vlastimil Babka wrote:
>> On 06/08/2017 09:45 AM, Michal Hocko wrote:
>>> From: Michal Hocko <mhocko@...e.com>
>>>
>>> alloc_huge_page_nodemask tries to allocate from any numa node in the
>>> allowed node mask. This might lead to filling up low NUMA nodes while
>>> others are not used. We can reduce this risk by introducing a concept
>>> of the preferred node similar to what we have in the regular page
>>> allocator. We will start allocating from the preferred nid and then
>>> iterate over all allowed nodes until we try them all. Introduce
>>> for_each_node_mask_preferred helper which does the iteration and reuse
>>> the available preferred node in new_page_nodemask which is currently
>>> the only caller of alloc_huge_page_nodemask.
>>>
>>> Signed-off-by: Michal Hocko <mhocko@...e.com>
>>
>> That's better, yeah. I don't think it would be too hard to use a
>> zonelist though. What do others think?
>
> OK, so I've given it a try. This is untested yet but it doesn't look all
> that bad. dequeue_huge_page_node will most proably see some clean up on
> top but I've kept it for simplicity for now.
> ---
> From 597ab787ac081b57db13ce5576700163d0c1208c Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@...e.com>
> Date: Wed, 7 Jun 2017 10:31:59 +0200
> Subject: [PATCH] hugetlb: add support for preferred node to
> alloc_huge_page_nodemask
>
> alloc_huge_page_nodemask tries to allocate from any numa node in the
> allowed node mask. This might lead to filling up low NUMA nodes while
> others are not used. We can reduce this risk by introducing a concept
> of the preferred node similar to what we have in the regular page
> allocator. We will start allocating from the preferred nid and then
> iterate over all allowed nodes in the zonelist order until we try them
> all.
>
> This is mimicking the page allocator logic except it operates on
> per-node mempools. dequeue_huge_page_vma already does this so distill
> the zonelist logic into a more generic dequeue_huge_page_nodemask
> and use it in alloc_huge_page_nodemask.
>
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
> include/linux/hugetlb.h | 3 +-
> include/linux/migrate.h | 2 +-
> mm/hugetlb.c | 111 +++++++++++++++++++++++++-----------------------
> 3 files changed, 60 insertions(+), 56 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index c469191bb13b..d4c33a8583be 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -349,7 +349,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> struct page *alloc_huge_page_node(struct hstate *h, int nid);
> struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
> unsigned long addr, int avoid_reserve);
> -struct page *alloc_huge_page_nodemask(struct hstate *h, const nodemask_t *nmask);
> +struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
> + nodemask_t *nmask);
> int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
> pgoff_t idx);
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index f80c9882403a..af3ccf93efaa 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -38,7 +38,7 @@ static inline struct page *new_page_nodemask(struct page *page, int preferred_ni
>
> if (PageHuge(page))
> return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
> - nodemask);
> + preferred_nid, nodemask);
>
> if (PageHighMem(page)
> || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 01c11ceb47d6..bbb3a1a46c64 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -897,29 +897,58 @@ static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
> return page;
> }
>
> -static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
> +/* Movability of hugepages depends on migration support. */
> +static inline gfp_t htlb_alloc_mask(struct hstate *h)
> {
> - struct page *page;
> - int node;
> + 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);
> +static struct page *dequeue_huge_page_nodemask(struct hstate *h, int nid,
> + nodemask_t *nmask)
> +{
> + unsigned int cpuset_mems_cookie;
> + struct zonelist *zonelist;
> + struct page *page = NULL;
> + struct zone *zone;
> + struct zoneref *z;
> + gfp_t gfp_mask;
> + int node = -1;
> +
> + gfp_mask = htlb_alloc_mask(h);
> + zonelist = node_zonelist(nid, gfp_mask);
> +
> +retry_cpuset:
> + cpuset_mems_cookie = read_mems_allowed_begin();
> + for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nmask) {
> + if (!cpuset_zone_allowed(zone, gfp_mask))
> + continue;
> + /*
> + * no need to ask again on the same node. Pool is node rather than
> + * zone aware
> + */
> + if (zone_to_nid(zone) == node)
> + continue;
> + node = zone_to_nid(zone);
>
> - for_each_online_node(node) {
> page = dequeue_huge_page_node_exact(h, node);
> if (page)
> - return page;
> + break;
> }
> + if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
> + goto retry_cpuset;
> +
> return NULL;
> }
>
> -/* 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.
> }
>
> static struct page *dequeue_huge_page_vma(struct hstate *h,
> @@ -927,15 +956,10 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
> unsigned long address, int avoid_reserve,
> long chg)
> {
> - struct page *page = NULL;
> + struct page *page;
> struct mempolicy *mpol;
> nodemask_t *nodemask;
> - gfp_t gfp_mask;
> int nid;
> - struct zonelist *zonelist;
> - struct zone *zone;
> - struct zoneref *z;
> - unsigned int cpuset_mems_cookie;
>
> /*
> * A child process with MAP_PRIVATE mappings created by their parent
> @@ -950,32 +974,14 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
> if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
> goto err;
>
> -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(...)) ?
> + SetPagePrivate(page);
> + h->resv_huge_pages--;
> }
>
> mpol_cond_put(mpol);
> - if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
> - goto retry_cpuset;
> return page;
>
> err:
> @@ -1723,29 +1729,26 @@ struct page *alloc_huge_page_node(struct hstate *h, int nid)
> return page;
> }
>
> -struct page *alloc_huge_page_nodemask(struct hstate *h, const nodemask_t *nmask)
> +struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
> + nodemask_t *nmask)
> {
> struct page *page = NULL;
> - int node;
>
> spin_lock(&hugetlb_lock);
> if (h->free_huge_pages - h->resv_huge_pages > 0) {
> - for_each_node_mask(node, *nmask) {
> - page = dequeue_huge_page_node_exact(h, node);
> - if (page)
> - break;
> - }
> + page = dequeue_huge_page_nodemask(h, preferred_nid, nmask);
> + if (page)
> + goto unlock;
> }
> +unlock:
> spin_unlock(&hugetlb_lock);
> if (page)
> return page;
>
> /* No reservations, try to overcommit */
> - for_each_node_mask(node, *nmask) {
> - page = __alloc_buddy_huge_page_no_mpol(h, node);
> - if (page)
> - return page;
> - }
> + page = __alloc_buddy_huge_page_no_mpol(h, preferred_nid);
> + if (page)
> + return page;
>
> return NULL;
> }
>
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