[dpdk-dev] Looks like rte_mempool_free_count() and rte_mempool_count() are swapped

[Dmitry Vyal]

Greetings.

I had a suspect I run into a mbuf depletion issue and decided to check 
using rte_mempool_free_count(). To my surprise, it returned a value 
equal to mempool size. I tried calling rte_mempool_count() and it 
returned zero.

I inspected the code in dpdk-1.3.1-7 and dpdk.1.4.1-4:

rte_mempool_count(const struct rte_mempool *mp)
{
     unsigned count;

     count = rte_ring_count(mp->ring);

#if RTE_MEMPOOL_CACHE_MAX_SIZE > 0
     {
         unsigned lcore_id;
         if (mp->cache_size == 0)
             return count;

         for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++)
             count += mp->local_cache[lcore_id].len;
     }
#endif

     /*
      * due to race condition (access to len is not locked), the
      * total can be greater than size... so fix the result
      */
     if (count > mp->size)
         return mp->size;
     return count;
}

If I understand it correctly, the ring contains free buffers and 
rte_ring_count() returns a number of entries inside a ring. So this 
function actually calculates the number of free entries, not busy.

Moreover, rte_mempool_count() is used in many places. For example it's 
called in rte_mempool_free_count() and rte_mempool_full().

Can anyone confirm or refute my findings?

Regards,
Dmitry