Re: [PATCH v8 20/23] tools/testing: Add support for prefilled slab sheafs

[Suren Baghdasaryan <surenb@google.com>]

On Wed, Sep 10, 2025 at 1:01 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@oracle.com>
>
> Add the prefilled sheaf structs to the slab header and the associated
> functions to the testing/shared/linux.c file.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Reviewed-by: Suren Baghdasaryan <surenb@google.com>

> ---
>  tools/include/linux/slab.h   | 28 ++++++++++++++
>  tools/testing/shared/linux.c | 89 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 117 insertions(+)
>
> diff --git a/tools/include/linux/slab.h b/tools/include/linux/slab.h
> index c5c5cc6db5668be2cc94c29065ccfa7ca7b4bb08..94937a699402bd1f31887dfb52b6fd0a3c986f43 100644
> --- a/tools/include/linux/slab.h
> +++ b/tools/include/linux/slab.h
> @@ -123,6 +123,18 @@ struct kmem_cache_args {
>         void (*ctor)(void *);
>  };
>
> +struct slab_sheaf {
> +       union {
> +               struct list_head barn_list;
> +               /* only used for prefilled sheafs */
> +               unsigned int capacity;
> +       };
> +       struct kmem_cache *cache;
> +       unsigned int size;
> +       int node; /* only used for rcu_sheaf */
> +       void *objects[];
> +};
> +
>  static inline void *kzalloc(size_t size, gfp_t gfp)
>  {
>         return kmalloc(size, gfp | __GFP_ZERO);
> @@ -173,5 +185,21 @@ __kmem_cache_create(const char *name, unsigned int size, unsigned int align,
>  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 97b8412ccbb6d222604c7b397c53c65618d8d51b..4ceff7969b78cf8e33cd1e021c68bc9f8a02a7a1 100644
> --- a/tools/testing/shared/linux.c
> +++ b/tools/testing/shared/linux.c
> @@ -137,6 +137,12 @@ void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t size, void **list)
>         if (kmalloc_verbose)
>                 pr_debug("Bulk free %p[0-%zu]\n", list, size - 1);
>
> +       if (cachep->exec_callback) {
> +               if (cachep->callback)
> +                       cachep->callback(cachep->private);
> +               cachep->exec_callback = false;
> +       }
> +
>         pthread_mutex_lock(&cachep->lock);
>         for (int i = 0; i < size; i++)
>                 kmem_cache_free_locked(cachep, list[i]);
> @@ -242,6 +248,89 @@ __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 (s->exec_callback) {
> +               if (s->callback)
> +                       s->callback(s->private);
> +               s->exec_callback = false;
> +       }
> +
> +       capacity = max(size, s->sheaf_capacity);
> +
> +       sheaf = calloc(1, sizeof(*sheaf) + sizeof(void *) * capacity);
> +       if (!sheaf)
> +               return NULL;
> +
> +       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)
> +               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)
> +{
> +       void *obj;
> +
> +       if (sheaf->size == 0) {
> +               printf("Nothing left in sheaf!\n");
> +               return NULL;
> +       }
> +
> +       obj = sheaf->objects[--sheaf->size];
> +       sheaf->objects[sheaf->size] = NULL;
> +
> +       return obj;
> +}
> +
>  /*
>   * Test the test infrastructure for kem_cache_alloc/free and bulk counterparts.
>   */
>
> --
> 2.51.0
>