2022-03-04 08:38:18

by Hyeonggon Yoo

Subject: [PATCH v2 4/5] mm/slub: limit number of node partial slabs only in cache creation

SLUB sets number of minimum partial slabs for node (min_partial)
using set_min_partial(). SLUB holds at least min_partial slabs even if
they're empty to avoid excessive use of page allocator.

set_min_partial() limits value of min_partial limits value of
min_partial MIN_PARTIAL and MAX_PARTIAL. As set_min_partial() can be
called by min_partial_store() too, Only limit value of min_partial
in kmem_cache_open() so that it can be changed to value that a user wants.

[ [email protected]: Fold set_min_partial() into its callers ]

Signed-off-by: Hyeonggon Yoo <[email protected]>
---
mm/slub.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 6f0ebadd8f30..f9ae983a3dc6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3981,15 +3981,6 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
return 1;
}

-static void set_min_partial(struct kmem_cache *s, unsigned long min)
-{
- if (min < MIN_PARTIAL)
- min = MIN_PARTIAL;
- else if (min > MAX_PARTIAL)
- min = MAX_PARTIAL;
- s->min_partial = min;
-}
-
static void set_cpu_partial(struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_CPU_PARTIAL
@@ -4196,7 +4187,8 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
* The larger the object size is, the more slabs we want on the partial
* list to avoid pounding the page allocator excessively.
*/
- set_min_partial(s, ilog2(s->size) / 2);
+ s->min_partial = min_t(unsigned long, MAX_PARTIAL, ilog2(s->size) / 2);
+ s->min_partial = max_t(unsigned long, MIN_PARTIAL, s->min_partial);

set_cpu_partial(s);

@@ -5361,7 +5353,7 @@ static ssize_t min_partial_store(struct kmem_cache *s, const char *buf,
if (err)
return err;

- set_min_partial(s, min);
+ s->min_partial = min;
return length;
}
SLAB_ATTR(min_partial);
--
2.33.1

2022-03-04 19:04:41

by Vlastimil Babka

Subject: Re: [PATCH v2 4/5] mm/slub: limit number of node partial slabs only in cache creation

On 3/4/22 07:34, Hyeonggon Yoo wrote:
> SLUB sets number of minimum partial slabs for node (min_partial)
> using set_min_partial(). SLUB holds at least min_partial slabs even if
> they're empty to avoid excessive use of page allocator.
>
> set_min_partial() limits value of min_partial limits value of
> min_partial MIN_PARTIAL and MAX_PARTIAL. As set_min_partial() can be
> called by min_partial_store() too, Only limit value of min_partial
> in kmem_cache_open() so that it can be changed to value that a user wants.
>
> [ [email protected]: Fold set_min_partial() into its callers ]
>
> Signed-off-by: Hyeonggon Yoo <[email protected]>

Reviewed-by: Vlastimil Babka <[email protected]>

> ---
> mm/slub.c | 14 +++-----------
> 1 file changed, 3 insertions(+), 11 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 6f0ebadd8f30..f9ae983a3dc6 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3981,15 +3981,6 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
> return 1;
> }
>
> -static void set_min_partial(struct kmem_cache *s, unsigned long min)
> -{
> - if (min < MIN_PARTIAL)
> - min = MIN_PARTIAL;
> - else if (min > MAX_PARTIAL)
> - min = MAX_PARTIAL;
> - s->min_partial = min;
> -}
> -
> static void set_cpu_partial(struct kmem_cache *s)
> {
> #ifdef CONFIG_SLUB_CPU_PARTIAL
> @@ -4196,7 +4187,8 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
> * The larger the object size is, the more slabs we want on the partial
> * list to avoid pounding the page allocator excessively.
> */
> - set_min_partial(s, ilog2(s->size) / 2);
> + s->min_partial = min_t(unsigned long, MAX_PARTIAL, ilog2(s->size) / 2);
> + s->min_partial = max_t(unsigned long, MIN_PARTIAL, s->min_partial);
>
> set_cpu_partial(s);
>
> @@ -5361,7 +5353,7 @@ static ssize_t min_partial_store(struct kmem_cache *s, const char *buf,
> if (err)
> return err;
>
> - set_min_partial(s, min);
> + s->min_partial = min;
> return length;
> }
> SLAB_ATTR(min_partial);