On Thursday 01 February 2018 03:44 PM, Olivier Matz wrote:
> On Thu, Feb 01, 2018 at 01:00:12PM +0300, Andrew Rybchenko wrote:
>> On 02/01/2018 12:30 PM, santosh wrote:
>>> On Thursday 01 February 2018 02:48 PM, Andrew Rybchenko wrote:
>>>> On 02/01/2018 12:09 PM, santosh wrote:
>>>>> On Thursday 01 February 2018 12:24 PM, Andrew Rybchenko wrote:
>>>>>> On 02/01/2018 08:05 AM, santosh wrote:
>>>>>>> On Wednesday 31 January 2018 10:15 PM, Olivier Matz wrote:
>>>>>>>> On Tue, Jan 23, 2018 at 01:15:56PM +0000, Andrew Rybchenko wrote:
>>>>>>>>> There is not specified dependency between
>>>>>>>>> rte_mempool_populate_default()
>>>>>>>>> and rte_mempool_populate_iova(). So, the second should not rely on the
>>>>>>>>> fact that the first adds capability flags to the mempool flags.
>>>>>>>>>
>>>>>>>>> Fixes: 65cf769f5e6a ("mempool: detect physical contiguous objects")
>>>>>>>>> Cc: sta...@dpdk.org
>>>>>>>>>
>>>>>>>>> Signed-off-by: Andrew Rybchenko <arybche...@solarflare.com>
>>>>>>>> Looks good to me. I agree it's strange that the mp->flags are
>>>>>>>> updated with capabilities only in rte_mempool_populate_default().
>>>>>>>> I see that this behavior is removed later in the patchset since the
>>>>>>>> get_capa() is removed!
>>>>>>>>
>>>>>>>> However maybe this single patch could go in 18.02.
>>>>>>>> +Santosh +Jerin since it's mostly about Octeon.
>>>>>>> rte_mempool_xmem_size should return correct size if
>>>>>>> MEMPOOL_F_CAPA_BLK_ALIGNED_OBJECTS flag
>>>>>>> is set in 'mp->flags'. Thats why _ops_get_capabilities() called in
>>>>>>> _populate_default() but not
>>>>>>> at _populate_iova().
>>>>>>> I think, this 'alone' patch may break octeontx mempool.
>>>>>> The patch does not touch rte_mempool_populate_default().
>>>>>> _ops_get_capabilities() is still called there before
>>>>>> rte_mempool_xmem_size(). The theoretical problem which
>>>>>> the patch tries to fix is the case when
>>>>>> rte_mempool_populate_default() is not called at all. I.e. application
>>>>>> calls _ops_get_capabilities() to get flags, then, together with
>>>>>> mp->flags, calls rte_mempool_xmem_size() directly, allocates
>>>>>> calculated amount of memory and calls _populate_iova().
>>>>>>
>>>>> In that case, Application does like below:
>>>>>
>>>>> /* Get mempool capabilities */
>>>>> mp_flags = 0;
>>>>> ret = rte_mempool_ops_get_capabilities(mp, &mp_flags);
>>>>> if ((ret < 0) && (ret != -ENOTSUP))
>>>>> return ret;
>>>>>
>>>>> /* update mempool capabilities */
>>>>> mp->flags |= mp_flags;
>>>> Above line is not mandatory. "mp->flags | mp_flags" could be simply
>>>> passed to rte_mempool_xmem_size() below.
>>>>
>>> That depends and again upto application requirement, if app further down
>>> wants to refer mp->flags for _align/_contig then better update to mp->flags.
>>>
>>> But that wasn't the point of discussion, I'm trying to understand that
>>> w/o this patch, whats could be the application level problem?
>> The problem that it is fragile. If application does not use
>> rte_mempool_populate_default() it has to care about addition
>> of mempool capability flags into mempool flags. If it is not done,
>> rte_mempool_populate_iova/virt/iova_tab() functions will work
>> incorrectly since F_CAPA_PHYS_CONTIG and
>> F_CAPA_BLK_ALIGNED_OBJECTS are missing.
>>
>> The idea of the patch is to make it a bit more robust. I have no
>> idea how it can break something. If capability flags are already
>> there - no problem. If no, just make sure that we locally have them.
> The example given by Santosh will work, but it is *not* the role of the
> application to update the mempool flags. And nothing says that it is mandatory
> to call rte_mempool_ops_get_capabilities() before the populate functions.
>
> For instance, in testpmd it calls rte_mempool_populate_anon() when using
> anonymous memory. The capabilities will never be updated in mp->flags.
Valid case and I agree with your example and explanation.
With nits change:
mp->flags |= mp_capa_flags;
Acked-by: Santosh Shukla <santosh.shu...@caviumnetworks.com>
