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

[fengchengwen]

Hi Mattias,

On 2022/10/7 3:53, Mattias Rönnblom wrote:
> 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."

+1

> 
> I assume they can be nested indefinitely?

Theoretically, yes.
And I'm going to add, to avoid loops

> 
>>
>> 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.

+1

> 
>> +        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;
>>   };
>>     /**
> 
> .