Re: [PATCH 2/11] hugetlb: add nodemask arg to huge page alloc, free and surplus adjust fcns

[David Rientjes <rientjes@google.com>]

On Mon, 5 Oct 2009, Lee Schermerhorn wrote:

> Index: linux-2.6.31-mmotm-090925-1435/mm/hugetlb.c
> ===================================================================
> --- linux-2.6.31-mmotm-090925-1435.orig/mm/hugetlb.c	2009-09-28 10:12:20.000000000 -0400
> +++ linux-2.6.31-mmotm-090925-1435/mm/hugetlb.c	2009-09-30 11:41:36.000000000 -0400
> @@ -622,48 +622,56 @@ static struct page *alloc_fresh_huge_pag
>  }
>  
>  /*
> - * common helper function for hstate_next_node_to_{alloc|free}.
> - * return next node in node_online_map, wrapping at end.
> + * common helper functions for hstate_next_node_to_{alloc|free}.
> + * We may have allocated or freed a huge page based on a different
> + * nodes_allowed previously, so h->next_node_to_{alloc|free} might
> + * be outside of *nodes_allowed.  Ensure that we use an allowed
> + * node for alloc or free.
>   */
> -static int next_node_allowed(int nid)
> +static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
>  {
> -	nid = next_node(nid, node_online_map);
> +	nid = next_node(nid, *nodes_allowed);
>  	if (nid == MAX_NUMNODES)
> -		nid = first_node(node_online_map);
> +		nid = first_node(*nodes_allowed);
>  	VM_BUG_ON(nid >= MAX_NUMNODES);
>  
>  	return nid;
>  }
>  
> +static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
> +{
> +	if (!node_isset(nid, *nodes_allowed))
> +		nid = next_node_allowed(nid, nodes_allowed);
> +	return nid;
> +}
> +
>  /*
> - * Use a helper variable to find the next node and then
> - * copy it back to next_nid_to_alloc afterwards:
> - * otherwise there's a window in which a racer might
> - * pass invalid nid MAX_NUMNODES to alloc_pages_exact_node.
> - * But we don't need to use a spin_lock here: it really
> - * doesn't matter if occasionally a racer chooses the
> - * same nid as we do.  Move nid forward in the mask even
> - * if we just successfully allocated a hugepage so that
> - * the next caller gets hugepages on the next node.
> + * returns the previously saved node ["this node"] from which to
> + * allocate a persistent huge page for the pool and advance the
> + * next node from which to allocate, handling wrap at end of node
> + * mask.
>   */
> -static int hstate_next_node_to_alloc(struct hstate *h)
> +static int hstate_next_node_to_alloc(struct hstate *h,
> +					nodemask_t *nodes_allowed)
>  {
> -	int nid, next_nid;
> +	int nid;
> +
> +	VM_BUG_ON(!nodes_allowed);
> +
> +	nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
> +	h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
>  
> -	nid = h->next_nid_to_alloc;
> -	next_nid = next_node_allowed(nid);
> -	h->next_nid_to_alloc = next_nid;
>  	return nid;
>  }
>  
> -static int alloc_fresh_huge_page(struct hstate *h)
> +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);
> +	start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
>  	next_nid = start_nid;
>  
>  	do {
> @@ -672,7 +680,7 @@ static int alloc_fresh_huge_page(struct
>  			ret = 1;
>  			break;
>  		}
> -		next_nid = hstate_next_node_to_alloc(h);
> +		next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
>  	} while (next_nid != start_nid);
>  
>  	if (ret)
> @@ -684,18 +692,20 @@ static int alloc_fresh_huge_page(struct
>  }
>  
>  /*
> - * helper for free_pool_huge_page() - return the next node
> - * from which to free a huge page.  Advance the next node id
> - * whether or not we find a free huge page to free so that the
> - * next attempt to free addresses the next node.
> + * helper for free_pool_huge_page() - return the previously saved
> + * node ["this node"] from which to free a huge page.  Advance the
> + * next node id whether or not we find a free huge page to free so
> + * that the next attempt to free addresses the next node.
>   */
> -static int hstate_next_node_to_free(struct hstate *h)
> +static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
>  {
> -	int nid, next_nid;
> +	int nid;
> +
> +	VM_BUG_ON(!nodes_allowed);
> +
> +	nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
> +	h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);
>  
> -	nid = h->next_nid_to_free;
> -	next_nid = next_node_allowed(nid);
> -	h->next_nid_to_free = next_nid;
>  	return nid;
>  }
>  
> @@ -705,13 +715,14 @@ static int hstate_next_node_to_free(stru
>   * balanced over allowed nodes.
>   * Called with hugetlb_lock locked.
>   */
> -static int free_pool_huge_page(struct hstate *h, bool acct_surplus)
> +static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
> +							 bool acct_surplus)
>  {
>  	int start_nid;
>  	int next_nid;
>  	int ret = 0;
>  
> -	start_nid = hstate_next_node_to_free(h);
> +	start_nid = hstate_next_node_to_free(h, nodes_allowed);
>  	next_nid = start_nid;
>  
>  	do {
> @@ -735,7 +746,7 @@ static int free_pool_huge_page(struct hs
>  			ret = 1;
>  			break;
>  		}
> -		next_nid = hstate_next_node_to_free(h);
> +		next_nid = hstate_next_node_to_free(h, nodes_allowed);
>  	} while (next_nid != start_nid);
>  
>  	return ret;
> @@ -937,7 +948,7 @@ static void return_unused_surplus_pages(
>  	 * on-line nodes for us and will handle the hstate accounting.
>  	 */
>  	while (nr_pages--) {
> -		if (!free_pool_huge_page(h, 1))
> +		if (!free_pool_huge_page(h, &node_online_map, 1))
>  			break;
>  	}
>  }
> @@ -1047,7 +1058,7 @@ int __weak alloc_bootmem_huge_page(struc
>  		void *addr;
>  
>  		addr = __alloc_bootmem_node_nopanic(
> -				NODE_DATA(hstate_next_node_to_alloc(h)),
> +				NODE_DATA(hstate_next_node_to_alloc(h, NULL)),
>  				huge_page_size(h), huge_page_size(h), 0);
>  
>  		if (addr) {
> @@ -1102,7 +1113,7 @@ static void __init hugetlb_hstate_alloc_
>  		if (h->order >= MAX_ORDER) {
>  			if (!alloc_bootmem_huge_page(h))
>  				break;
> -		} else if (!alloc_fresh_huge_page(h))
> +		} else if (!alloc_fresh_huge_page(h, &node_online_map))
>  			break;
>  	}
>  	h->max_huge_pages = i;
> @@ -1144,16 +1155,22 @@ static void __init report_hugepages(void
>  }
>  
>  #ifdef CONFIG_HIGHMEM
> -static void try_to_free_low(struct hstate *h, unsigned long count)
> +static void try_to_free_low(struct hstate *h, unsigned long count,
> +						nodemask_t *nodes_allowed)
>  {
>  	int i;
>  
>  	if (h->order >= MAX_ORDER)
>  		return;
>  
> +	if (!nodes_allowed)
> +		nodes_allowed = &node_online_map;
> +
>  	for (i = 0; i < MAX_NUMNODES; ++i) {
>  		struct page *page, *next;
>  		struct list_head *freel = &h->hugepage_freelists[i];
> +		if (!node_isset(i, *nodes_allowed))
> +			continue;
>  		list_for_each_entry_safe(page, next, freel, lru) {
>  			if (count >= h->nr_huge_pages)
>  				return;

Simply converting the iteration to use
for_each_node_mask(i, *nodes_allowed) would be cleaner.

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