[dpdk-dev] [PATCH v3 2/2] ethdev: allow pmd to advertise pool handle

[santosh]

Hi Olivier,


On Monday 04 September 2017 05:41 PM, Olivier MATZ wrote:
> Hi Santosh,
>
> On Tue, Aug 15, 2017 at 01:37:17PM +0530, Santosh Shukla wrote:
>> Now that dpdk supports more than one mempool drivers and
>> each mempool driver works best for specific PMD, example:
>> - sw ring based mempool for Intel PMD drivers
>> - dpaa2 HW mempool manager for dpaa2 PMD driver.
>> - fpa HW mempool manager for Octeontx PMD driver.
>>
>> Application like to know `preferred mempool vs PMD driver`
>> information in advance before port setup.
>>
>> Introducing rte_eth_dev_get_preferred_pool_ops() API,
>> which allows PMD driver to advertise their pool capability to application.
>>
>> Application side programing sequence would be:
>>
>> char pref_mempool[RTE_MEMPOOL_OPS_NAMESIZE];
>> rte_eth_dev_get_preferred_pool_ops(ethdev_port_id, pref_mempoolx /*out*/);
>> rte_mempool_create_empty();
>> rte_mempool_set_ops_byname( , pref_memppol, );
>> rte_mempool_populate_default();
>>
>> Signed-off-by: Santosh Shukla <santosh.shukla at caviumnetworks.com>
>> ---
>> v2 --> v3:
>> - Updated version.map entry to DPDK_v17.11.
>>
>> v1 --> v2:
>> - Renamed _get_preferred_pool to _get_preferred_pool_ops().
>> Per v1 review feedback, Olivier suggested to rename api
>> to rte_eth_dev_pool_ops_supported(), considering that 2nd param
>> for that api will return pool handle 'priority' for that port.
>> However, per v1 [1], we're opting for approach 1) where
>> ethdev API returns _preferred_ pool handle to application and Its upto
>> application to decide on policy - whether application wants to create
>> pool with received preferred pool handle or not. For more discussion details
>> on this topic refer [1].
> Well, I still think it would be more flexible to have an API like
>  rte_eth_dev_pool_ops_supported(uint8_t port_id, const char *pool)
>
> It supports the easy case (= one preferred mempool) without much pain,
> and provides a more precise manner to describe what is supported or not
> by the driver. Example: "pmd_foo" prefers "mempool_foo" (best perf), but
> also supporst "mempool_stack" and "mempool_ring", but "mempool_bar"
> won't work at all.
>
> Having only one preferred pool_ops also prevents from smoothly renaming
> a pool (supporting both during some time) or to have 2 names for
> different variants of the same pool_ops (ex: ring_mp_mc, ring_sp_sc).
>
> But if the users (I guess at least Cavium and NXP) are happy with
> what you propose, I'm fine with it.

preferred handle based upon real world use-case and same thing raised
at [1].

Hi Hemant, Are you ok with proposed preferred API?

[1] http://dpdk.org/dev/patchwork/patch/24944/

>> --- a/lib/librte_ether/rte_ethdev.c
>> +++ b/lib/librte_ether/rte_ethdev.c
>> @@ -3409,3 +3409,21 @@ rte_eth_dev_adjust_nb_rx_tx_desc(uint8_t port_id,
>>  
>>  	return 0;
>>  }
>> +
>> +int
>> +rte_eth_dev_get_preferred_pool_ops(uint8_t port_id, char *pool)
>> +{
>> +	struct rte_eth_dev *dev;
>> +	const char *tmp;
>> +
>> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
>> +
>> +	dev = &rte_eth_devices[port_id];
>> +
>> +	if (*dev->dev_ops->get_preferred_pool_ops == NULL) {
>> +		tmp = rte_eal_mbuf_default_mempool_ops();
>> +		snprintf(pool, RTE_MBUF_POOL_OPS_NAMESIZE, "%s", tmp);
>> +		return 0;
>> +	}
>> +	return (*dev->dev_ops->get_preferred_pool_ops)(dev, pool);
>> +}
> I think adding the length of the pool buffer to the function arguments
> would be better: only documenting that the length is
> RTE_MBUF_POOL_OPS_NAMESIZE looks a bit weak to me, because if one day it
> changes to another value, the users of the function may not notice it
> (no ABI/API change).
>
>
> One more comment: it would be helpful to have one user of this API in
> the example apps or testpmd.

Yes. I will add in v3. Thanks.

> Olivier