linux-kernel - Re: [PATCH v4 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to

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Date: Mon, 22 Jan 2024 14:16:30 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Gang Li <gang.li@...ux.dev>, David Hildenbrand <david@...hat.com>,
 David Rientjes <rientjes@...gle.com>, Mike Kravetz
 <mike.kravetz@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Tim Chen <tim.c.chen@...ux.intel.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 ligang.bdlg@...edance.com
Subject: Re: [PATCH v4 4/7] hugetlb: pass *next_nid_to_alloc directly to
 for_each_node_mask_to_alloc



On 2024/1/18 20:39, Gang Li wrote:
> With parallelization of hugetlb allocation across different threads, each
> thread works on a differnet node to allocate pages from, instead of all
> allocating from a common node h->next_nid_to_alloc.  To address this, it's
> necessary to assign a separate next_nid_to_alloc for each thread.
>
> Consequently, the hstate_next_node_to_alloc and for_each_node_mask_to_alloc
> have been modified to directly accept a *next_nid_to_alloc parameter,
> ensuring thread-specific allocation and avoiding concurrent access issues.
>
> Signed-off-by: Gang Li <gang.li@...ux.dev>
> Tested-by: David Rientjes <rientjes@...gle.com>
> ---
>   mm/hugetlb.c | 22 ++++++++++++----------
>   1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 98ae108e1fac..effe5539e545 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1464,15 +1464,15 @@ static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
>    * 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(int *next_node,
>   					nodemask_t *nodes_allowed)
>   {
>   	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 = get_valid_node_allowed(*next_node, nodes_allowed);
> +	*next_node = next_node_allowed(nid, nodes_allowed);
>   
>   	return nid;
>   }
> @@ -1495,10 +1495,10 @@ 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)		\
> +#define for_each_node_mask_to_alloc(next_node, nr_nodes, node, mask)		\
>   	for (nr_nodes = nodes_weight(*mask);				\
>   		nr_nodes > 0 &&						\
> -		((node = hstate_next_node_to_alloc(hs, mask)) || 1);	\
> +		((node = hstate_next_node_to_alloc(next_node, mask)) || 1);	\
>   		nr_nodes--)
>   
>   #define for_each_node_mask_to_free(hs, nr_nodes, node, mask)		\
> @@ -2350,12 +2350,13 @@ static void prep_and_add_allocated_folios(struct hstate *h,
>    */
>   static struct folio *alloc_pool_huge_folio(struct hstate *h,
>   					nodemask_t *nodes_allowed,
> -					nodemask_t *node_alloc_noretry)
> +					nodemask_t *node_alloc_noretry,
> +					int *next_node)
>   {
>   	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
>   	int nr_nodes, node;
>   
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +	for_each_node_mask_to_alloc(next_node, nr_nodes, node, nodes_allowed) {


A small question here, why not pass h->next_nid_to_alloc to
for_each_node_mask_to_alloc()? What's the purpose of the third
parameter of alloc_pool_huge_folio()?

Thanks.