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Message-ID: <66af5bce84c9b6480feaa2ddaff199cd5722fcde.camel@linux.intel.com>
Subject: Re: [PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to
 for_each_node_mask_to_alloc
From: Tim Chen <tim.c.chen@linux.intel.com>
To: Gang Li <gang.li@linux.dev>, David Hildenbrand <david@redhat.com>, David
 Rientjes <rientjes@google.com>, Mike Kravetz <mike.kravetz@oracle.com>,
 Muchun Song <muchun.song@linux.dev>, Andrew Morton
 <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 ligang.bdlg@bytedance.com
Date: Thu, 11 Jan 2024 14:21:42 -0800
In-Reply-To: <20240102131249.76622-5-gang.li@linux.dev>
References: <20240102131249.76622-1-gang.li@linux.dev>
	 <20240102131249.76622-5-gang.li@linux.dev>
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On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
> The parallelization of hugetlb allocation leads to errors when sharing
> h->next_nid_to_alloc across different threads. To address this, it's

Suggest you say
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.
>=20
> Consequently, the hstate_next_node_to_alloc and for_each_node_mask_to_all=
oc
> have been modified to directly accept a *next_nid_to_alloc parameter,
> ensuring thread-specific allocation and avoiding concurrent access issues=
.
>=20
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
> This patch seems not elegant, but I can't come up with anything better.
> Any suggestions will be highly appreciated!
> ---
>  mm/hugetlb.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
>=20
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 92448e747991d..a71bc1622b53b 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1464,15 +1464,15 @@ static int get_valid_node_allowed(int nid, nodema=
sk_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_nid_to_alloc,
>  					nodemask_t *nodes_allowed)
>  {
>  	int nid;
> =20
>  	VM_BUG_ON(!nodes_allowed);
> =20
> -	nid =3D get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
> -	h->next_nid_to_alloc =3D next_node_allowed(nid, nodes_allowed);
> +	nid =3D get_valid_node_allowed(*next_nid_to_alloc, nodes_allowed);
> +	*next_nid_to_alloc =3D next_node_allowed(nid, nodes_allowed);
> =20
>  	return nid;
>  }
> @@ -1495,10 +1495,10 @@ static int hstate_next_node_to_free(struct hstate=
 *h, nodemask_t *nodes_allowed)
>  	return nid;
>  }
> =20
> -#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask)		\
> +#define for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, m=
ask)		\
>  	for (nr_nodes =3D nodes_weight(*mask);				\
>  		nr_nodes > 0 &&						\
> -		((node =3D hstate_next_node_to_alloc(hs, mask)) || 1);	\
> +		((node =3D hstate_next_node_to_alloc(next_nid_to_alloc, mask)) || 1);	=
\
>  		nr_nodes--)
> =20
>  #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_nid_to_alloc)
>  {
>  	gfp_t gfp_mask =3D htlb_alloc_mask(h) | __GFP_THISNODE;
>  	int nr_nodes, node;
> =20
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +	for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, nodes_al=
lowed) {
>  		struct folio *folio;
> =20
>  		folio =3D only_alloc_fresh_hugetlb_folio(h, gfp_mask, node,
> @@ -3310,7 +3311,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int=
 nid)
>  		goto found;
>  	}
>  	/* allocate from next node when distributing huge pages */
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) =
{
> +	for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &nod=
e_states[N_MEMORY]) {
>  		m =3D memblock_alloc_try_nid_raw(
>  				huge_page_size(h), huge_page_size(h),
>  				0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
> @@ -3684,7 +3685,7 @@ static int adjust_pool_surplus(struct hstate *h, no=
demask_t *nodes_allowed,
>  	VM_BUG_ON(delta !=3D -1 && delta !=3D 1);
> =20
>  	if (delta < 0) {
> -		for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +		for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, nod=
es_allowed) {
>  			if (h->surplus_huge_pages_node[node])
>  				goto found;
>  		}
> @@ -3799,7 +3800,8 @@ static int set_max_huge_pages(struct hstate *h, uns=
igned long count, int nid,
>  		cond_resched();
> =20
>  		folio =3D alloc_pool_huge_folio(h, nodes_allowed,
> -						node_alloc_noretry);
> +						node_alloc_noretry,
> +						&h->next_nid_to_alloc);
>  		if (!folio) {
>  			prep_and_add_allocated_folios(h, &page_list);
>  			spin_lock_irq(&hugetlb_lock);