On Wed, Jul 08, 2009 at 03:24:38PM -0400, Lee Schermerhorn wrote:
> [PATCH 1/3] hugetlb: add nodemask arg to huge page alloc, free and surplus adjust fcns
>
> Against: 25jun09 mmotm atop the "hugetlb: balance freeing..." series
>
> In preparation for constraining huge page allocation and freeing by the
> controlling task's numa mempolicy, add a "nodes_allowed" nodemask pointer
> to the allocate, free and surplus adjustment functions. For now, pass
> NULL to indicate default behavior--i.e., use node_online_map. A
> subsqeuent patch will derive a non-default mask from the controlling
> task's numa mempolicy.
>
> Note the "cleanup" in alloc_bootmem_huge_page(): always advance next nid,
> even if allocation succeeds. I believe that this is correct behavior,
> and I'll replace it in the next patch which assumes this behavior.
> However, perhaps the current code is correct: we only want to advance
> bootmem huge page allocation to the next node when we've exhausted all
> huge pages on the current hstate "next_node_to_alloc". Any who understands
> the rationale for this: please advise.
>
I think we covered this up in V1. What I said at the time was
I strongly suspect that the same node being used until allocation
failure instead of round-robin is an oversight and not deliberate
at all. I can't think of a good reason for boot-allocation to behave
significantly different to runtime-allocation.
But I looked briefly into it a bit more now. Maybe you could change the
changelog to say the following?
==== CUT HERE ====
Note the "cleanup" in alloc_bootmem_huge_page(): always advance next nid,
even if allocation succeeds. I believe that this is correct behavior,
and I'll replace it in the next patch which assumes this behavior.
According to Mel Gorman;
I strongly suspect that the same node being used until allocation
failure instead of round-robin is an oversight and not deliberate
at all. It appears to be a side-effect of a fix made way back in
commit 63b4613c3f0d4b724ba259dc6c201bb68b884e1a ["hugetlb: fix
hugepage allocation with memoryless nodes"]. Prior to that patch
it looked like allocations would always round-robin even when
allocation was successful.
==== CUT HERE ====
> Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
>
Other then the comment "/* always advance nid */" being on the same line
as the code and one minor piece of whitespace damage I point out below,
I can't see any problem with the patch.
Reviewed-by: Mel Gorman <mel@xxxxxxxxx>
> mm/hugetlb.c | 51 +++++++++++++++++++++++++++++++--------------------
> 1 file changed, 31 insertions(+), 20 deletions(-)
>
> Index: linux-2.6.31-rc1-mmotm-090625-1549/mm/hugetlb.c
> ===================================================================
> --- linux-2.6.31-rc1-mmotm-090625-1549.orig/mm/hugetlb.c 2009-07-07 09:58:13.000000000 -0400
> +++ linux-2.6.31-rc1-mmotm-090625-1549/mm/hugetlb.c 2009-07-07 09:58:17.000000000 -0400
> @@ -631,17 +631,22 @@ static struct page *alloc_fresh_huge_pag
> * if we just successfully allocated a hugepage so that
> * the next caller gets hugepages on the next node.
> */
> -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 next_nid;
> - next_nid = next_node(h->next_nid_to_alloc, node_online_map);
> +
> + if (!nodes_allowed)
> + nodes_allowed = &node_online_map;
> +
> + next_nid = next_node(h->next_nid_to_alloc, *nodes_allowed);
> if (next_nid == MAX_NUMNODES)
> - next_nid = first_node(node_online_map);
> + next_nid = first_node(*nodes_allowed);
> h->next_nid_to_alloc = next_nid;
> return next_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;
> @@ -655,7 +660,7 @@ static int alloc_fresh_huge_page(struct
> page = alloc_fresh_huge_page_node(h, next_nid);
> if (page)
> ret = 1;
> - next_nid = hstate_next_node_to_alloc(h);
> + next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> } while (!page && next_nid != start_nid);
>
> if (ret)
> @@ -670,12 +675,16 @@ static int alloc_fresh_huge_page(struct
> * helper for free_pool_huge_page() - find next node
> * from which to free a huge page
> */
> -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 next_nid;
> - next_nid = next_node(h->next_nid_to_free, node_online_map);
> +
> + if (!nodes_allowed)
> + nodes_allowed = &node_online_map;
> +
> + next_nid = next_node(h->next_nid_to_free, *nodes_allowed);
> if (next_nid == MAX_NUMNODES)
> - next_nid = first_node(node_online_map);
> + next_nid = first_node(*nodes_allowed);
> h->next_nid_to_free = next_nid;
> return next_nid;
> }
> @@ -686,7 +695,8 @@ 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;
> @@ -715,7 +725,7 @@ static int free_pool_huge_page(struct hs
> update_and_free_page(h, page);
> ret = 1;
> }
> - next_nid = hstate_next_node_to_free(h);
> + next_nid = hstate_next_node_to_free(h, nodes_allowed);
There is minor whitespace damage there - specifically space at the
beginning of the line.
> } while (!ret && next_nid != start_nid);
>
> return ret;
> @@ -917,7 +927,7 @@ 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, NULL, 1))
> break;
> }
> }
> @@ -1030,6 +1040,7 @@ int __weak alloc_bootmem_huge_page(struc
> NODE_DATA(h->next_nid_to_alloc),
> huge_page_size(h), huge_page_size(h), 0);
>
> + hstate_next_node_to_alloc(h, NULL); /* always advance nid */
> if (addr) {
> /*
> * Use the beginning of the huge page to store the
> @@ -1039,7 +1050,6 @@ int __weak alloc_bootmem_huge_page(struc
> m = addr;
> goto found;
> }
> - hstate_next_node_to_alloc(h);
> nr_nodes--;
> }
> return 0;
> @@ -1083,7 +1093,7 @@ 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, NULL))
> break;
> }
> h->max_huge_pages = i;
> @@ -1158,7 +1168,8 @@ static inline void try_to_free_low(struc
> * balanced by operating on them in a round-robin fashion.
> * Returns 1 if an adjustment was made.
> */
> -static int adjust_pool_surplus(struct hstate *h, int delta)
> +static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
> + int delta)
> {
> int start_nid, next_nid;
> int ret = 0;
> @@ -1174,7 +1185,7 @@ static int adjust_pool_surplus(struct hs
> do {
> int nid = next_nid;
> if (delta < 0) {
> - next_nid = hstate_next_node_to_alloc(h);
> + next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> /*
> * To shrink on this node, there must be a surplus page
> */
> @@ -1182,7 +1193,7 @@ static int adjust_pool_surplus(struct hs
> continue;
> }
> if (delta > 0) {
> - next_nid = hstate_next_node_to_free(h);
> + next_nid = hstate_next_node_to_free(h, nodes_allowed);
> /*
> * Surplus cannot exceed the total number of pages
> */
> @@ -1221,7 +1232,7 @@ static unsigned long set_max_huge_pages(
> */
> spin_lock(&hugetlb_lock);
> while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
> - if (!adjust_pool_surplus(h, -1))
> + if (!adjust_pool_surplus(h, NULL, -1))
> break;
> }
>
> @@ -1232,7 +1243,7 @@ static unsigned long set_max_huge_pages(
> * and reducing the surplus.
> */
> spin_unlock(&hugetlb_lock);
> - ret = alloc_fresh_huge_page(h);
> + ret = alloc_fresh_huge_page(h, NULL);
> spin_lock(&hugetlb_lock);
> if (!ret)
> goto out;
> @@ -1258,11 +1269,11 @@ static unsigned long set_max_huge_pages(
> min_count = max(count, min_count);
> try_to_free_low(h, min_count);
> while (min_count < persistent_huge_pages(h)) {
> - if (!free_pool_huge_page(h, 0))
> + if (!free_pool_huge_page(h, NULL, 0))
> break;
> }
> while (count < persistent_huge_pages(h)) {
> - if (!adjust_pool_surplus(h, 1))
> + if (!adjust_pool_surplus(h, NULL, 1))
> break;
> }
> out:
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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