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Message-ID: <20130722162336.GJ24400@dhcp22.suse.cz>
Date: Mon, 22 Jul 2013 18:23:36 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Hugh Dickins <hughd@...gle.com>,
Davidlohr Bueso <davidlohr.bueso@...com>,
David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>
Subject: Re: [PATCH v2 05/10] mm, hugetlb: fix and clean-up node iteration
code to alloc or free
On Mon 22-07-13 17:36:26, Joonsoo Kim wrote:
> Current node iteration code have a minor problem which do one more
> node rotation if we can't succeed to allocate. For example,
> if we start to allocate at node 0, we stop to iterate at node 0.
> Then we start to allocate at node 1 for next allocation.
>
> I introduce new macros "for_each_node_mask_to_[alloc|free]" and
> fix and clean-up node iteration code to alloc or free.
> This makes code more understandable.
I don't know but it feels like you are trying to fix an awkward
interface with another one. Why hstate_next_node_to_alloc cannot simply
return MAX_NUMNODES once the loop is done and start from first_node next
time it is called? We wouldn't have the bug you are mentioning and you
do not need scary looking macros.
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 83edd17..3ac0a6f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -752,33 +752,6 @@ static int hstate_next_node_to_alloc(struct hstate *h,
> return nid;
> }
>
> -static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
> -{
> - struct page *page;
> - int start_nid;
> - int next_nid;
> - int ret = 0;
> -
> - start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> - next_nid = start_nid;
> -
> - do {
> - page = alloc_fresh_huge_page_node(h, next_nid);
> - if (page) {
> - ret = 1;
> - break;
> - }
> - next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> - } while (next_nid != start_nid);
> -
> - if (ret)
> - count_vm_event(HTLB_BUDDY_PGALLOC);
> - else
> - count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
> -
> - return ret;
> -}
> -
> /*
> * helper for free_pool_huge_page() - return the previously saved
> * node ["this node"] from which to free a huge page. Advance the
> @@ -797,6 +770,40 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
> return nid;
> }
>
> +#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask) \
> + for (nr_nodes = nodes_weight(*mask); \
> + nr_nodes > 0 && \
> + ((node = hstate_next_node_to_alloc(hs, mask)) || 1); \
> + nr_nodes--)
> +
> +#define for_each_node_mask_to_free(hs, nr_nodes, node, mask) \
> + for (nr_nodes = nodes_weight(*mask); \
> + nr_nodes > 0 && \
> + ((node = hstate_next_node_to_free(hs, mask)) || 1); \
> + nr_nodes--)
> +
> +static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
> +{
> + struct page *page;
> + int nr_nodes, node;
> + int ret = 0;
> +
> + for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> + page = alloc_fresh_huge_page_node(h, node);
> + if (page) {
> + ret = 1;
> + break;
> + }
> + }
> +
> + if (ret)
> + count_vm_event(HTLB_BUDDY_PGALLOC);
> + else
> + count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
> +
> + return ret;
> +}
> +
> /*
> * Free huge page from pool from next node to free.
> * Attempt to keep persistent huge pages more or less
> @@ -806,36 +813,31 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
> static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
> bool acct_surplus)
> {
> - int start_nid;
> - int next_nid;
> + int nr_nodes, node;
> int ret = 0;
>
> - start_nid = hstate_next_node_to_free(h, nodes_allowed);
> - next_nid = start_nid;
> -
> - do {
> + for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
> /*
> * If we're returning unused surplus pages, only examine
> * nodes with surplus pages.
> */
> - if ((!acct_surplus || h->surplus_huge_pages_node[next_nid]) &&
> - !list_empty(&h->hugepage_freelists[next_nid])) {
> + if ((!acct_surplus || h->surplus_huge_pages_node[node]) &&
> + !list_empty(&h->hugepage_freelists[node])) {
> struct page *page =
> - list_entry(h->hugepage_freelists[next_nid].next,
> + list_entry(h->hugepage_freelists[node].next,
> struct page, lru);
> list_del(&page->lru);
> h->free_huge_pages--;
> - h->free_huge_pages_node[next_nid]--;
> + h->free_huge_pages_node[node]--;
> if (acct_surplus) {
> h->surplus_huge_pages--;
> - h->surplus_huge_pages_node[next_nid]--;
> + h->surplus_huge_pages_node[node]--;
> }
> update_and_free_page(h, page);
> ret = 1;
> break;
> }
> - next_nid = hstate_next_node_to_free(h, nodes_allowed);
> - } while (next_nid != start_nid);
> + }
>
> return ret;
> }
> @@ -1172,14 +1174,12 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
> int __weak alloc_bootmem_huge_page(struct hstate *h)
> {
> struct huge_bootmem_page *m;
> - int nr_nodes = nodes_weight(node_states[N_MEMORY]);
> + int nr_nodes, node;
>
> - while (nr_nodes) {
> + for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> void *addr;
>
> - addr = __alloc_bootmem_node_nopanic(
> - NODE_DATA(hstate_next_node_to_alloc(h,
> - &node_states[N_MEMORY])),
> + addr = __alloc_bootmem_node_nopanic(NODE_DATA(node),
> huge_page_size(h), huge_page_size(h), 0);
>
> if (addr) {
> @@ -1191,7 +1191,6 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
> m = addr;
> goto found;
> }
> - nr_nodes--;
> }
> return 0;
>
> @@ -1330,48 +1329,28 @@ static inline void try_to_free_low(struct hstate *h, unsigned long count,
> static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
> int delta)
> {
> - int start_nid, next_nid;
> - int ret = 0;
> + int nr_nodes, node;
>
> VM_BUG_ON(delta != -1 && delta != 1);
>
> - if (delta < 0)
> - start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> - else
> - start_nid = hstate_next_node_to_free(h, nodes_allowed);
> - next_nid = start_nid;
> -
> - do {
> - int nid = next_nid;
> - if (delta < 0) {
> - /*
> - * To shrink on this node, there must be a surplus page
> - */
> - if (!h->surplus_huge_pages_node[nid]) {
> - next_nid = hstate_next_node_to_alloc(h,
> - nodes_allowed);
> - continue;
> - }
> + if (delta < 0) {
> + for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> + if (h->surplus_huge_pages_node[node])
> + goto found;
> }
> - if (delta > 0) {
> - /*
> - * Surplus cannot exceed the total number of pages
> - */
> - if (h->surplus_huge_pages_node[nid] >=
> - h->nr_huge_pages_node[nid]) {
> - next_nid = hstate_next_node_to_free(h,
> - nodes_allowed);
> - continue;
> - }
> + } else {
> + for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
> + if (h->surplus_huge_pages_node[node] <
> + h->nr_huge_pages_node[node])
> + goto found;
> }
> + }
> + return 0;
>
> - h->surplus_huge_pages += delta;
> - h->surplus_huge_pages_node[nid] += delta;
> - ret = 1;
> - break;
> - } while (next_nid != start_nid);
> -
> - return ret;
> +found:
> + h->surplus_huge_pages += delta;
> + h->surplus_huge_pages_node[node] += delta;
> + return 1;
> }
>
> #define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
> --
> 1.7.9.5
>
--
Michal Hocko
SUSE Labs
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