Re: [dpdk-dev] [PATCH v4 2/4] mempool: add non-IO flag

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 10/15/21 12:18 PM, Dmitry Kozlyuk wrote:
>> -----Original Message-----
>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>> [...]
>>> diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
>>> index 51c0ba2931..2204f140b3 100644
>>> --- a/lib/mempool/rte_mempool.c
>>> +++ b/lib/mempool/rte_mempool.c
>>> @@ -371,6 +371,8 @@ rte_mempool_populate_iova(struct rte_mempool *mp,
>>> char *vaddr,
>>>
>>>       STAILQ_INSERT_TAIL(&mp->mem_list, memhdr, next);
>>>       mp->nb_mem_chunks++;
>>> +     if (iova == RTE_BAD_IOVA)
>>> +             mp->flags |= MEMPOOL_F_NON_IO;
>>
>> As I understand rte_mempool_populate_iova() may be called few times for
>> one mempool. The flag must be set if all invocations are done with
>> RTE_BAD_IOVA. So, it should be set by default and just removed when iova
>> != RTE_BAD_IOVA happens.
> 
> I don't agree at all. If any object of the pool is unsuitable for IO,
> the pool cannot be considered suitable for IO. So if there's a single
> invocation with RTE_BAD_IOVA, the flag must be set forever.

If so, some objects may be used for IO, some cannot be used.
What should happen if an application allocates an object
which is suitable for IO and try to use it this way?

> 
>> Yes, it is a corner case. May be it makes sense to cover it by unit test
>> as well.
> 
> True for either your logic or mine, I'll add it.
> 
> Ack on the rest of the comments, thanks.
>