[Mesa-dev] [PATCH 3/7] util/slab: Add function to flush allocations from a child pool

[Haehnle, Nicolai]

On 21.11.18 01:39, Ian Romanick wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
> 
> Ralloc has a feature that all allocations from a temporary memory
> context can be whisked away in a single call without fear of leaks.  As
> the slab allocator is designed for use in multhreaded scenarios with a
> child pool per CPU, it lacks this feature.  However, many users will be
> single threaded with a single child pool.  For these users, we can have
> our cake and eat it too.
> 
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> Cc: Nicolai Hähnle <nicolai.haehnle at amd.com>
> ---
>   src/util/slab.c | 21 +++++++++++++++++++++
>   src/util/slab.h |  1 +
>   2 files changed, 22 insertions(+)
> 
> diff --git a/src/util/slab.c b/src/util/slab.c
> index 5f048666b56..1bcc1db6e09 100644
> --- a/src/util/slab.c
> +++ b/src/util/slab.c
> @@ -172,6 +172,27 @@ void slab_destroy_child(struct slab_child_pool *pool)
>      pool->parent = NULL;
>   }
>   
> +/**
> + * Flush all allocations from a pool.  Single-threaded (no mutex).
> + */
> +void
> +slab_flush_st(struct slab_mempool *parent)

The name of the function argument should be "pool" for consistency.

> +{
> +   struct slab_child_pool *const pool = &parent->child;
> +
> +   assert(pool->migrated == NULL);
> +   assert(pool->parent == parent);

I'm surprised this works. Why isn't pool->parent == &parent->parent?

Or, with a consistently named function argument, why isn't 
pool->child.parent == &pool->parent?

The intention of the patch looks fine though.

Cheers,
Nicolai


> +
> +   while (pool->pages) {
> +      struct slab_page_header *page = pool->pages;
> +      pool->pages = page->u.next;
> +
> +      free(page);
> +   }
> +
> +   pool->free = NULL;
> +}
> +
>   static bool
>   slab_add_new_page(struct slab_child_pool *pool)
>   {
> diff --git a/src/util/slab.h b/src/util/slab.h
> index e83f8ec1a0e..a4279d8e65b 100644
> --- a/src/util/slab.h
> +++ b/src/util/slab.h
> @@ -90,5 +90,6 @@ void slab_create(struct slab_mempool *pool,
>   void slab_destroy(struct slab_mempool *pool);
>   void *slab_alloc_st(struct slab_mempool *pool);
>   void slab_free_st(struct slab_mempool *pool, void *ptr);
> +void slab_flush_st(struct slab_mempool *parent);
>   
>   #endif
>