On 3/11/26 1:52 PM, Konstantin Ananyev wrote:
On 3/10/26 5:10 PM, Morten Brørup wrote:
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.
I guess ring is involved in fact since the default mempool driver is
ring.
See drivers/mempool/ring/rte_mempool_ring.c ring_alloc().
Yes, it is not ideal, but at least it explains why RTE_RING_NAMESIZE
is used.
Thanks, that explains it. Bad layer violation...
Let's hope no future mempool driver adds anything longer than "RG_" to the
name of any memzone it creates.
Looking into the associated string length checks, using a too long name will
fail
with ENAMETOOLONG.
So, using a long mempool name might succeed with some mempool drivers and
fail with others. :-(
I guess there's no simple fix for that.
And I was wrong to think that the RTE_MEMPOOL_NAMESIZE should be
increased from 26 to 29.
As a generic thought: might be it is time to make the length across these
structs (mempool, ring, etc.) arbitrary?
At our next big API breakage or so.
Why not, if it is really required
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
