Re: [dpdk-dev] [PATCH v2] mempool: reduce rte_mempool structure size

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Keith,

On 02/10/2016 07:35 PM, Wiles, Keith wrote:
>>> @@ -672,6 +704,24 @@ rte_mempool_count(const struct rte_mempool *mp)
>>>  static unsigned
>>>  rte_mempool_dump_cache(FILE *f, const struct rte_mempool *mp)
>>>  {
>>> +#ifdef RTE_NEXT_ABI
>>> +	unsigned lcore_id;
>>> +	unsigned count = 0;
>>> +	unsigned cache_count;
>>> +
>>> +	fprintf(f, "  cache infos:\n");
>>> +	fprintf(f, "    cache_size=%"PRIu32"\n", mp->cache_size);
>>> +	if (mp->cache_size == 0)
>>> +		return count;
>>> +
>>> +	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
>>> +		cache_count = mp->local_cache[lcore_id].len;
>>> +		fprintf(f, "    cache_count[%u]=%u\n", lcore_id, cache_count);
>>> +		count += cache_count;
>>> +	}
>>> +	fprintf(f, "    total_cache_count=%u\n", count);
>>> +	return count;
>>> +#else
>>>  #if RTE_MEMPOOL_CACHE_MAX_SIZE > 0
>>>  	unsigned lcore_id;
>>>  	unsigned count = 0;
>>
>> I think in this case we could avoid to duplicate the code without
>> beeing unclear by using the proper #ifdefs:
>>
>> #if RTE_MEMPOOL_CACHE_MAX_SIZE > 0 || defined(RTE_NEXT_ABI)
>> 	/* common code */
>> #ifdef RTE_NEXT_ABI
>> 	if (mp->cache_size == 0)
>> 		return count;
>> #endif
>> 	/* common code */
>> #else
>> ...
>> #endif
> 
> Started looking at this change and the problem is I want to remove the ifdef RTE_MEMPOOL.. As well as the #else/#endif code. If I do as you suggest it does not appear to be clearer when someone goes back to remove the code, they may think the #ifdef RTE_MEMPOOL/#else/#endif are still required.

OK, makes sense.

>>> @@ -755,19 +793,25 @@ static inline void __attribute__((always_inline))
>>>  __mempool_put_bulk(struct rte_mempool *mp, void * const *obj_table,
>>>  		    unsigned n, int is_mp)
>>>  {
>>> +#ifndef RTE_NEXT_ABI	/* Note: ifndef */
>>>  #if RTE_MEMPOOL_CACHE_MAX_SIZE > 0
>>> +#endif /* RTE_NEXT_ABI */
>>>  	struct rte_mempool_cache *cache;
>>>  	uint32_t index;
>>>  	void **cache_objs;
>>>  	unsigned lcore_id = rte_lcore_id();
>>>  	uint32_t cache_size = mp->cache_size;
>>>  	uint32_t flushthresh = mp->cache_flushthresh;
>>> +#ifndef RTE_NEXT_ABI	/* Note: ifndef */
>>>  #endif /* RTE_MEMPOOL_CACHE_MAX_SIZE > 0 */
>>> +#endif /* RTE_NEXT_ABI */
>>
>> this looks strange... I think it does not work properly.
>> Why not
>> #if RTE_MEMPOOL_CACHE_MAX_SIZE > 0 || defined(RTE_NEXT_ABI)
> 
> Yes I agree the ifndef looks strange, but it should work as we want to remove the #ifdef RTE_MEMPOOL/#endif lines. This was the reason for the comment that it was a ifndef.

It's not only strange, it's also probably not what you want to do:

	#ifndef RTE_NEXT_ABI	/* Note: ifndef */
	#if RTE_MEMPOOL_CACHE_MAX_SIZE > 0
	#endif /* RTE_NEXT_ABI */
	...

Here, the #endif corresponds to the second #if, not the first #ifdef.

Regards,
Olivier