mempool name size incorrect?

[Morten Brørup]

Isn't the RTE_MEMPOOL_NAMESIZE too short?

Looking at the names sizes:

RTE_MEMZONE_NAMESIZE = 32,
RTE_RING_NAMESIZE = RTE_MEMZONE_NAMESIZE - (sizeof("RG_")=4) + 1 = 29,
RTE_MEMPOOL_NAMESIZE = RTE_RING_NAMESIZE - (sizeof("MP_")=4) + 1 = 26

Referring to [1], I think it should be fixed as:
- #define RTE_MEMPOOL_NAMESIZE (RTE_RING_NAMESIZE - \
			      sizeof(RTE_MEMPOOL_MZ_PREFIX) + 1)
+ #define RTE_MEMPOOL_NAMESIZE (RTE_MEMZONE_NAMESIZE - \
			      sizeof(RTE_MEMPOOL_MZ_PREFIX) + 1)

There is no ring involved, so I guess it is some kind of copy-paste-search-replace error.


Looking at the rte_mempool structure [2]:
struct __rte_cache_aligned rte_mempool {
	char name[RTE_MEMPOOL_NAMESIZE]; /**< Name of mempool. */
	union {
		void *pool_data;         /**< Ring or pool to store objects. */
		uint64_t pool_id;        /**< External mempool identifier. */
	};


Due to the 8-byte alignment of the pool_id field following the name field, fixing the length as suggested doesn't change the memory layout for 64 bit CPU architectures.
But it does for 32 bit CPU architectures, which will only 4-byte align the pool_id field.

[1]: https://elixir.bootlin.com/dpdk/v26.03-rc1/source/lib/mempool/rte_mempool.h#L128
[2]: https://elixir.bootlin.com/dpdk/v26.03-rc1/source/lib/mempool/rte_mempool.h#L230


Another thing:
On 32 bit CPU architectures, the cache_size and local_cache fields in the rte_mempool structure are not in the same cache line.
But I guess we don't really care about 32 bit CPU architectures.


Venlig hilsen / Kind regards,
-Morten Brørup