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!
>
> Thanks,
> Olivier
>
