Re: [PATCH 4/9] mm, hugetlb: fix and clean-up node iteration code to alloc or free

Joonsoo Kim
2013-07-18T06:46:31Z

On Wed, Jul 17, 2013 at 10:00:48AM +0800, Jianguo Wu wrote:
> On 2013/7/15 17:52, 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.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 0067cf4..a838e6b 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 +770,42 @@ 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), \
> > + node = hstate_next_node_to_alloc(hs, mask); \
> > + nr_nodes > 0 && \
> > + ((node = hstate_next_node_to_alloc(hs, mask)) || 1); \
>
> Hi Joonsoo,

Hello, Jianguo.

>
> For the first loop, node = hstate_next_node_to_alloc() will be executed two times,
> so will skip the first node in mask, right?

Yes, it's my fault.
I will fix it on v2.

Thanks.

>
> Thanks,
> Jianguo Wu.
>
> > + nr_nodes--)
> > +
> > +#define for_each_node_mask_to_free(hs, nr_nodes, node, mask) \
> > + for (nr_nodes = nodes_weight(*mask), \
> > + node = hstate_next_node_to_free(hs, 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 +815,31 @@ 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;
> > }
> > @@ -1173,14 +1177,12 @@ 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) {
> > @@ -1192,7 +1194,6 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
> > m = addr;
> > goto found;
> > }
> > - nr_nodes--;
> > }
> > return 0;
> >
> > @@ -1331,48 +1332,28 @@ 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)
>
>
>
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