[dpdk-dev] [PATCH v2] mempool: adjust name string size in related data types

[Olivier Matz]

On 07/21/2016 03:47 PM, Zoltan Kiss wrote:
> 
> 
> On 21/07/16 14:40, Olivier Matz wrote:
>> Hi Zoltan,
>>
>>
>> On 07/20/2016 07:16 PM, Zoltan Kiss wrote:
>>> A recent patch brought up an issue about the size of the 'name' fields:
>>>
>>> 85cf0079 mem: avoid memzone/mempool/ring name truncation
>>>
>>> These relations should be observed:
>>>
>>> 1. Each ring creates a memzone with a prefixed name:
>>> RTE_RING_NAMESIZE <= RTE_MEMZONE_NAMESIZE - strlen(RTE_RING_MZ_PREFIX)
>>>
>>> 2. There are some mempool handlers which create a ring with a prefixed
>>> name:
>>> RTE_MEMPOOL_NAMESIZE <= RTE_RING_NAMESIZE -
>>> strlen(RTE_MEMPOOL_MZ_PREFIX)
>>>
>>> 3. A mempool can create up to RTE_MAX_MEMZONE pre and postfixed
>>> memzones:
>>> sprintf(postfix, "_%d", RTE_MAX_MEMZONE)
>>> RTE_MEMPOOL_NAMESIZE <= RTE_MEMZONE_NAMESIZE -
>>>     strlen(RTE_MEMPOOL_MZ_PREFIX) - strlen(postfix)
>>>
>>> Setting all of them to 32 hides this restriction from the application.
>>> This patch decreases the mempool and ring string size to accommodate for
>>> these prefixes, but it doesn't apply the 3rd constraint. Applications
>>> relying on these constants need to be recompiled, otherwise they'll run
>>> into ENAMETOOLONG issues.
>>> The size of the arrays are kept 32 for ABI compatibility, it can be
>>> decreased next time the ABI changes.
>>>
>>> Signed-off-by: Zoltan Kiss <zoltan.kiss at schaman.hu>
>>
>> Looks like to be a good compromise for the 16.07 release. One question
>> however: why not taking in account the 3rd constraint? Because it may
>> not completly fix the issue if the mempool is fragmented.
>>
>> We could define RTE_MEMPOOL_NAMESIZE to 24
>>  = 32 - len('mp_') - len('_0123'))
> 
> I was trying to figure out a compile time macro for strlen(postfix), but
> I could not. Your suggestion would work only until someone increases
> RTE_MAX_MEMZONE above 9999. As the likelihood of fragmenting a pool over
> 99 memzones seems small, I did not bother to fix this with an ugly hack,
> but if you think we should include it, let me know!

Ok, looks fair, thanks for the clarification.

Acked-by: Olivier Matz <olivier.matz at 6wind.com>