Re: [PATCH v5 06/14] tools: Add sheaves support to testing infrastructure

[Suren Baghdasaryan <surenb@google.com>]

On Wed, Jul 23, 2025 at 6:35 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
>
> Allocate a sheaf and fill it to the count amount.  Does not fill to the
> sheaf limit to detect incorrect allocation requests.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>  tools/include/linux/slab.h   | 24 +++++++++++++
>  tools/testing/shared/linux.c | 84 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 108 insertions(+)
>
> diff --git a/tools/include/linux/slab.h b/tools/include/linux/slab.h
> index d1444e79f2685edb828adbce8b3fbb500c0f8844..1962d7f1abee154e1cda5dba28aef213088dd198 100644
> --- a/tools/include/linux/slab.h
> +++ b/tools/include/linux/slab.h
> @@ -23,6 +23,13 @@ enum slab_state {
>         FULL
>  };
>
> +struct slab_sheaf {
> +       struct kmem_cache *cache;
> +       unsigned int size;
> +       unsigned int capacity;
> +       void *objects[];
> +};
> +
>  struct kmem_cache_args {
>         unsigned int align;
>         unsigned int sheaf_capacity;
> @@ -80,4 +87,21 @@ void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t size, void **list);
>  int kmem_cache_alloc_bulk(struct kmem_cache *cachep, gfp_t gfp, size_t size,
>                           void **list);
>
> +struct slab_sheaf *
> +kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size);
> +
> +void *
> +kmem_cache_alloc_from_sheaf(struct kmem_cache *s, gfp_t gfp,
> +               struct slab_sheaf *sheaf);
> +
> +void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp,
> +               struct slab_sheaf *sheaf);
> +int kmem_cache_refill_sheaf(struct kmem_cache *s, gfp_t gfp,
> +               struct slab_sheaf **sheafp, unsigned int size);
> +
> +static inline unsigned int kmem_cache_sheaf_size(struct slab_sheaf *sheaf)
> +{
> +       return sheaf->size;
> +}
> +
>  #endif         /* _TOOLS_SLAB_H */
> diff --git a/tools/testing/shared/linux.c b/tools/testing/shared/linux.c
> index f998555a1b2af4a899a468a652b04622df459ed3..e0255f53159bd3a1325d49192283dd6790a5e3b8 100644
> --- a/tools/testing/shared/linux.c
> +++ b/tools/testing/shared/linux.c
> @@ -181,6 +181,12 @@ int kmem_cache_alloc_bulk(struct kmem_cache *cachep, gfp_t gfp, size_t size,
>         if (kmalloc_verbose)
>                 pr_debug("Bulk alloc %zu\n", size);
>
> +       if (cachep->exec_callback) {
> +               if (cachep->callback)
> +                       cachep->callback(cachep->private);
> +               cachep->exec_callback = false;
> +       }
> +
>         pthread_mutex_lock(&cachep->lock);
>         if (cachep->nr_objs >= size) {
>                 struct radix_tree_node *node;
> @@ -270,6 +276,84 @@ __kmem_cache_create_args(const char *name, unsigned int size,
>         return ret;
>  }
>
> +struct slab_sheaf *
> +kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
> +{
> +       struct slab_sheaf *sheaf;
> +       unsigned int capacity;
> +
> +       if (size > s->sheaf_capacity)
> +               capacity = size;
> +       else
> +               capacity = s->sheaf_capacity;

nit:
capacity = max(size, s->sheaf_capacity);

> +
> +       sheaf = malloc(sizeof(*sheaf) + sizeof(void *) * s->sheaf_capacity * capacity);

Should this really be `sizeof(void *) * s->sheaf_capacity * capacity`
or just `sizeof(void *) * capacity` ?


> +       if (!sheaf) {
> +               return NULL;
> +       }
> +
> +       memset(sheaf, 0, size);
> +       sheaf->cache = s;
> +       sheaf->capacity = capacity;
> +       sheaf->size = kmem_cache_alloc_bulk(s, gfp, size, sheaf->objects);
> +       if (!sheaf->size) {
> +               free(sheaf);
> +               return NULL;
> +       }
> +
> +       return sheaf;
> +}
> +
> +int kmem_cache_refill_sheaf(struct kmem_cache *s, gfp_t gfp,
> +                struct slab_sheaf **sheafp, unsigned int size)
> +{
> +       struct slab_sheaf *sheaf = *sheafp;
> +       int refill;
> +
> +       if (sheaf->size >= size)
> +               return 0;
> +
> +       if (size > sheaf->capacity) {
> +               sheaf = kmem_cache_prefill_sheaf(s, gfp, size);
> +               if (!sheaf)
> +                       return -ENOMEM;
> +
> +               kmem_cache_return_sheaf(s, gfp, *sheafp);
> +               *sheafp = sheaf;
> +               return 0;
> +       }
> +
> +       refill = kmem_cache_alloc_bulk(s, gfp, size - sheaf->size,
> +                                      &sheaf->objects[sheaf->size]);
> +       if (!refill)
> +               return -ENOMEM;
> +
> +       sheaf->size += refill;
> +       return 0;
> +}
> +
> +void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp,
> +                struct slab_sheaf *sheaf)
> +{
> +       if (sheaf->size) {
> +               //s->non_kernel += sheaf->size;

Above comment seems obsolete.

> +               kmem_cache_free_bulk(s, sheaf->size, &sheaf->objects[0]);
> +       }
> +       free(sheaf);
> +}
> +
> +void *
> +kmem_cache_alloc_from_sheaf(struct kmem_cache *s, gfp_t gfp,
> +               struct slab_sheaf *sheaf)
> +{
> +       if (sheaf->size == 0) {
> +               printf("Nothing left in sheaf!\n");
> +               return NULL;
> +       }
> +

Should we clear sheaf->objects[sheaf->size] for additional safety?

> +       return sheaf->objects[--sheaf->size];
> +}
> +
>  /*
>   * Test the test infrastructure for kem_cache_alloc/free and bulk counterparts.
>   */
>
> --
> 2.50.1
>