[dpdk-dev] [PATCH v2] mempool: replace c memcpy code semantics with optimized rte_memcpy
Olivier MATZ
olivier.matz at 6wind.com
Tue May 31 23:05:30 CEST 2016
Hi Jerin,
>>> /* Add elements back into the cache */
>>> - for (index = 0; index < n; ++index, obj_table++)
>>> - cache_objs[index] = *obj_table;
>>> + rte_memcpy(&cache_objs[0], obj_table, sizeof(void *) * n);
>>>
>>> cache->len += n;
>>>
>>>
>>
>> I also checked in the get_bulk() function, which looks like that:
>>
>> /* Now fill in the response ... */
>> for (index = 0, len = cache->len - 1;
>> index < n;
>> ++index, len--, obj_table++)
>> *obj_table = cache_objs[len];
>>
>> I think we could replace it by something like:
>>
>> rte_memcpy(obj_table, &cache_objs[len - n], sizeof(void *) * n);
>>
>> The only difference is that it won't reverse the pointers in the
>> table, but I don't see any problem with that.
>>
>> What do you think?
>
> In true sense, it will _not_ be LIFO. Not sure about cache usage implications
> on the specific use cases.
Today, the objects pointers are reversed only in the get(). It means
that this code:
rte_mempool_get_bulk(mp, table, 4);
for (i = 0; i < 4; i++)
printf("obj = %p\n", t[i]);
rte_mempool_put_bulk(mp, table, 4);
printf("-----\n");
rte_mempool_get_bulk(mp, table, 4);
for (i = 0; i < 4; i++)
printf("obj = %p\n", t[i]);
rte_mempool_put_bulk(mp, table, 4);
prints:
addr1
addr2
addr3
addr4
-----
addr4
addr3
addr2
addr1
Which is quite strange.
I don't think it would be an issue to replace the loop by a
rte_memcpy(), it may increase the copy speed and it will be
more coherent with the put().
Olivier
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