[PATCH v5 07/10] memarea: support backup memory mechanism

[Mattias Rönnblom]

On 2022-10-05 06:09, datshan wrote:
> From: Chengwen Feng <fengchengwen at huawei.com>
> 
> This patch supports backup memory mechanism, the memarea could use
> another memarea as a backup.

Maybe it's worth mentioning what backup means already here.

"This patch adds a memarea backup mechanism, where an allocation request 
which cannot be met by a certain memarea is deferred to its backup memarea."

I assume they can be nested indefinitely?

> 
> Signed-off-by: Chengwen Feng <fengchengwen at huawei.com>
> ---
>   doc/guides/prog_guide/memarea_lib.rst |  3 +++
>   lib/memarea/memarea_private.h         |  2 ++
>   lib/memarea/rte_memarea.c             | 22 ++++++++++++++++++++++
>   lib/memarea/rte_memarea.h             |  7 +++++++
>   4 files changed, 34 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/memarea_lib.rst b/doc/guides/prog_guide/memarea_lib.rst
> index c77012fe44..842d35f77a 100644
> --- a/doc/guides/prog_guide/memarea_lib.rst
> +++ b/doc/guides/prog_guide/memarea_lib.rst
> @@ -25,6 +25,9 @@ The main features are as follows:
>   
>   * It supports MT-safe as long as it's specified at creation time.
>   
> +* It provides backup memory mechanism, the memarea could use another memarea
> +  as a backup.
> +
>   Library API Overview
>   --------------------
>   
> diff --git a/lib/memarea/memarea_private.h b/lib/memarea/memarea_private.h
> index 98406879b9..08735ca81f 100644
> --- a/lib/memarea/memarea_private.h
> +++ b/lib/memarea/memarea_private.h
> @@ -23,11 +23,13 @@ struct rte_memarea {
>   	struct rte_memarea_param init;
>   	rte_spinlock_t           lock;
>   	void                    *area_addr;
> +	void                    *top_addr;
>   	struct memarea_elem_list elem_list;
>   	struct memarea_elem_list free_list;
>   
>   	uint64_t alloc_fails;
>   	uint64_t refcnt_check_fails;
> +	uint64_t bak_alloc_fails;
>   } __rte_cache_aligned;
>   
>   #endif /* MEMAREA_PRIVATE_H */
> diff --git a/lib/memarea/rte_memarea.c b/lib/memarea/rte_memarea.c
> index b70830d0bb..f45191aa7f 100644
> --- a/lib/memarea/rte_memarea.c
> +++ b/lib/memarea/rte_memarea.c
> @@ -132,6 +132,7 @@ rte_memarea_create(const struct rte_memarea_param *init)
>   	TAILQ_INIT(&ma->elem_list);
>   	TAILQ_INIT(&ma->free_list);
>   	ma->area_addr = addr;
> +	ma->top_addr = (void *)((uintptr_t)addr + init->total_sz - 1);

RTE_PTR_ADD()

>   	elem = addr;
>   	elem->size = init->total_sz - sizeof(struct memarea_elem);
>   	elem->cookie = MEMAREA_FREE_ELEM_COOKIE;
> @@ -200,6 +201,15 @@ memarea_add_node(struct rte_memarea *ma, struct memarea_elem *elem, size_t need_
>   	elem->size = align_size;
>   }
>   
> +static inline void *
> +memarea_alloc_backup(struct rte_memarea *ma, size_t size, uint32_t cookie)
> +{
> +	void *ptr = rte_memarea_alloc(ma->init.bak_memarea, size, cookie);
> +	if (unlikely(ptr == NULL))
> +		ma->bak_alloc_fails++;
> +	return ptr;
> +}
> +
>   void *
>   rte_memarea_alloc(struct rte_memarea *ma, size_t size, uint32_t cookie)
>   {
> @@ -221,6 +231,8 @@ rte_memarea_alloc(struct rte_memarea *ma, size_t size, uint32_t cookie)
>   		ptr = (void *)((uintptr_t)elem + sizeof(struct memarea_elem));
>   		break;
>   	}
> +	if (ptr == NULL && ma->init.bak_memarea != NULL)

Maybe you want an unlikely() around the above, too. I assume using the 
backup area is an exceptional case.

> +		ptr = memarea_alloc_backup(ma, size, cookie);
>   	if (unlikely(ptr == NULL))
>   		ma->alloc_fails++;
>   	memarea_unlock(ma);
> @@ -283,6 +295,12 @@ rte_memarea_update_refcnt(struct rte_memarea *ma, void *ptr, int16_t value)
>   		return;
>   
>   	memarea_lock(ma);
> +	if (ptr < ma->area_addr || ptr > ma->top_addr) {
> +		rte_memarea_update_refcnt(ma->init.bak_memarea, ptr, value);
> +		memarea_unlock(ma);
> +		return;
> +	}
> +
>   	if (unlikely(elem->refcnt <= 0 || elem->refcnt + value < 0)) {
>   		RTE_LOG(ERR, MEMAREA,
>   			"memarea: %s cookie: 0x%x curr refcnt: %d update refcnt: %d check fail!\n",
> @@ -373,10 +391,14 @@ rte_memarea_dump(struct rte_memarea *ma, FILE *f, bool dump_all)
>   	fprintf(f, "  algorithm: %s\n", memarea_alg_name(ma->init.alg));
>   	fprintf(f, "  total-size: 0x%zx\n", ma->init.total_sz);
>   	fprintf(f, "  mt-safe: %s\n", ma->init.mt_safe ? "yes" : "no");
> +	if (ma->init.bak_memarea)
> +		fprintf(f, "  backup-memarea-name: %s\n", ma->init.bak_memarea->init.name);
>   	fprintf(f, "  total-regions: %u\n", memarea_elem_list_num(ma));
>   	fprintf(f, "  total-free-regions: %u\n", memarea_free_list_num(ma));
>   	fprintf(f, "  alloc_fails: %" PRIu64 "\n", ma->alloc_fails);
>   	fprintf(f, "  refcnt_check_fails: %" PRIu64 "\n", ma->refcnt_check_fails);
> +	if (ma->init.bak_memarea)
> +		fprintf(f, "  backup_alloc_fails: %" PRIu64 "\n", ma->bak_alloc_fails);
>   	if (dump_all)
>   		memarea_dump_all(ma, f);
>   	memarea_unlock(ma);
> diff --git a/lib/memarea/rte_memarea.h b/lib/memarea/rte_memarea.h
> index 10b8229c64..348febab7f 100644
> --- a/lib/memarea/rte_memarea.h
> +++ b/lib/memarea/rte_memarea.h
> @@ -39,6 +39,9 @@
>    *   specified, all the functions of the memarea API are lock-free, and assume
>    *   to not be invoked in parallel on different logical cores to work on the
>    *   same memarea.
> + * - It provides backup memory mechanism, the memarea could use another memarea
> + *   as a backup. It will attempts to allocate object from backup memarea when
> + *   the current memarea failed to allocate.
>    */
>   
>   #include <stdbool.h>
> @@ -105,6 +108,10 @@ struct rte_memarea_param {
>   		 */
>   		struct rte_memarea *user_memarea;
>   	};
> +	/** Backup memarea, which is used to handle the scenario where the
> +	 * current memarea allocation failure.
> +	 */
> +	struct rte_memarea *bak_memarea;
>   };
>   
>   /**