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[PATCH 3/9] rhashtable: simplify a strange allocation pattern

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  [PATCH 3/9] rhashtable: simplify a strange allocation pattern Michal Hocko <mhocko@kernel.org> - 2017-01-30 11:00 +0100
    Re: [PATCH 3/9] rhashtable: simplify a strange allocation pattern Vlastimil Babka <vbabka@suse.cz> - 2017-01-30 15:10 +0100

#1569506 — [PATCH 3/9] rhashtable: simplify a strange allocation pattern

From: Michal Hocko <mhocko@suse.com>

alloc_bucket_locks allocation pattern is quite unusual. We are
preferring vmalloc when CONFIG_NUMA is enabled. The rationale is that
vmalloc will respect the memory policy of the current process and so the
backing memory will get distributed over multiple nodes if the requester
is configured properly. At least that is the intention, in reality
rhastable is shrunk and expanded from a kernel worker so no mempolicy
can be assumed.

Let's just simplify the code and use kvmalloc helper, which is a
transparent way to use kmalloc with vmalloc fallback, if the caller
is allowed to block and use the flag otherwise.

Cc: Tom Herbert <tom@herbertland.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 lib/rhashtable.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 32d0ad058380..1a487ea70829 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -77,16 +77,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
 	size = min_t(unsigned int, size, tbl->size >> 1);
 
 	if (sizeof(spinlock_t) != 0) {
-		tbl->locks = NULL;
-#ifdef CONFIG_NUMA
-		if (size * sizeof(spinlock_t) > PAGE_SIZE &&
-		    gfp == GFP_KERNEL)
-			tbl->locks = vmalloc(size * sizeof(spinlock_t));
-#endif
-		if (gfp != GFP_KERNEL)
-			gfp |= __GFP_NOWARN | __GFP_NORETRY;
-
-		if (!tbl->locks)
+		if (gfpflags_allow_blocking(gfp))
+			tbl->locks = kvmalloc(size * sizeof(spinlock_t), gfp);
+		else
 			tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
 						   gfp);
 		if (!tbl->locks)
-- 
2.11.0

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#1569762

On 01/30/2017 10:49 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> alloc_bucket_locks allocation pattern is quite unusual. We are
> preferring vmalloc when CONFIG_NUMA is enabled. The rationale is that
> vmalloc will respect the memory policy of the current process and so the
> backing memory will get distributed over multiple nodes if the requester
> is configured properly. At least that is the intention, in reality
> rhastable is shrunk and expanded from a kernel worker so no mempolicy
> can be assumed.
>
> Let's just simplify the code and use kvmalloc helper, which is a
> transparent way to use kmalloc with vmalloc fallback, if the caller
> is allowed to block and use the flag otherwise.
>
> Cc: Tom Herbert <tom@herbertland.com>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
>  lib/rhashtable.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/lib/rhashtable.c b/lib/rhashtable.c
> index 32d0ad058380..1a487ea70829 100644
> --- a/lib/rhashtable.c
> +++ b/lib/rhashtable.c
> @@ -77,16 +77,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
>  	size = min_t(unsigned int, size, tbl->size >> 1);
>
>  	if (sizeof(spinlock_t) != 0) {
> -		tbl->locks = NULL;
> -#ifdef CONFIG_NUMA
> -		if (size * sizeof(spinlock_t) > PAGE_SIZE &&
> -		    gfp == GFP_KERNEL)
> -			tbl->locks = vmalloc(size * sizeof(spinlock_t));
> -#endif
> -		if (gfp != GFP_KERNEL)
> -			gfp |= __GFP_NOWARN | __GFP_NORETRY;
> -
> -		if (!tbl->locks)
> +		if (gfpflags_allow_blocking(gfp))
> +			tbl->locks = kvmalloc(size * sizeof(spinlock_t), gfp);
> +		else
>  			tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
>  						   gfp);
>  		if (!tbl->locks)
>

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