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Subject: mempool name size incorrect?
Date: Tue, 10 Mar 2026 15:10:35 +0100
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35F65773@smartserver.smartshare.dk>
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Thread-Topic: mempool name size incorrect?
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Andrew Rybchenko" <andrew.rybchenko@oktetlabs.ru>,
	<dev@dpdk.org>
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Isn't the RTE_MEMPOOL_NAMESIZE too short?

Looking at the names sizes:

RTE_MEMZONE_NAMESIZE =3D 32,
RTE_RING_NAMESIZE =3D RTE_MEMZONE_NAMESIZE - (sizeof("RG_")=3D4) + 1 =3D =
29,
RTE_MEMPOOL_NAMESIZE =3D RTE_RING_NAMESIZE - (sizeof("MP_")=3D4) + 1 =3D =
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 Br=F8rup