Re: [dpdk-dev] [PATCH] ethdev: add queue state when retrieve queue information

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

On 3/22/21 6:45 PM, Ananyev, Konstantin wrote:
> 
> 
>> -----Original Message-----
>> From: dev <dev-bounces@dpdk.org> On Behalf Of Andrew Rybchenko
>> Sent: Monday, March 22, 2021 2:49 PM
>> To: Yigit, Ferruh <ferruh.yigit@intel.com>; Lijun Ou <oulijun@huawei.com>; thomas@monjalon.net
>> Cc: dev@dpdk.org; linuxarm@openeuler.org; Andrew Rybchenko <arybchenko@solarflare.com>; David Marchand
>> <david.marchand@redhat.com>; Ray Kinsella <mdr@ashroe.eu>; Luca Boccassi <bluca@debian.org>
>> Subject: Re: [dpdk-dev] [PATCH] ethdev: add queue state when retrieve queue information
>>
>> On 3/22/21 12:22 PM, Ferruh Yigit wrote:
>>> On 3/18/2021 12:25 PM, Lijun Ou wrote:
>>>> Currently, upper-layer application could get queue state only
>>>> through pointers such as dev->data->tx_queue_state[queue_id],
>>>> this is not the recommended way to access it. So this patch
>>>> add get queue state when call rte_eth_rx_queue_info_get and
>>>> rte_eth_tx_queue_info_get API.
>>>>
>>>> Note: The hairpin queue is not supported with above
>>>> rte_eth_*x_queue_info_get, so the queue state could be
>>>> RTE_ETH_QUEUE_STATE_STARTED or RTE_ETH_QUEUE_STATE_STOPPED.
>>>> Note: After add queue_state field, the 'struct rte_eth_rxq_info' size
>>>> remains 128B, and the 'struct rte_eth_txq_info' size remains 64B, so
>>>> it could be ABI compatible.
>>>>
>>>> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
>>>> Signed-off-by: Lijun Ou <oulijun@huawei.com>
>>>
>>> <...>
>>>
>>>> diff --git a/lib/librte_ethdev/rte_ethdev.h
>>>> b/lib/librte_ethdev/rte_ethdev.h
>>>> index efda313..3b83c5a 100644
>>>> --- a/lib/librte_ethdev/rte_ethdev.h
>>>> +++ b/lib/librte_ethdev/rte_ethdev.h
>>>> @@ -1591,6 +1591,8 @@ struct rte_eth_rxq_info {
>>>>       uint8_t scattered_rx;       /**< scattered packets RX supported. */
>>>>       uint16_t nb_desc;           /**< configured number of RXDs. */
>>>>       uint16_t rx_buf_size;       /**< hardware receive buffer size. */
>>>> +    /**< Queues state: STARTED(1) / STOPPED(0). */
>>>> +    uint8_t queue_state;
>>>>   } __rte_cache_min_aligned;
>>>>     /**
>>>> @@ -1600,6 +1602,8 @@ struct rte_eth_rxq_info {
>>>>   struct rte_eth_txq_info {
>>>>       struct rte_eth_txconf conf; /**< queue config parameters. */
>>>>       uint16_t nb_desc;           /**< configured number of TXDs. */
>>>> +    /**< Queues state: STARTED(1) / STOPPED(0). */
>>>> +    uint8_t queue_state;
>>>>   } __rte_cache_min_aligned;
>>>>     /* Generic Burst mode flag definition, values can be ORed. */
>>>>
>>>
>>> This is causing an ABI warning [1], but I guess it is safe since the
>>> size of the struct is not changing (cache align). Adding a few more
>>> people to comment.
>>>
>>>
>>> [1]
>>> https://travis-ci.com/github/ovsrobot/dpdk/builds/220497651
>>
>> Frankly speaking I dislike addition of queue_state as uint8_t.
>> IMHO it should be either 'bool started' or enum to support more
>> states in the future if we need.
> 
> I think we already have set of defines for it:
> lib/librte_ethdev/rte_ethdev_driver.h:925:#define RTE_ETH_QUEUE_STATE_STOPPED 0
> lib/librte_ethdev/rte_ethdev_driver.h:926:#define RTE_ETH_QUEUE_STATE_STARTED 1
> lib/librte_ethdev/rte_ethdev_driver.h:927:#define RTE_ETH_QUEUE_STATE_HAIRPIN 2
> 
> If we want to publish it, then might be enough just move these macros to rte_ethdev.h or so.
> 
> About uint8_t vs enum - yes, in principle enum would be a bit nicer,
> but right now rte_eth_dev_data.(rx|tx)_queue_state[]  itself is an array of uint8_t.
> So probably not much point to waste extra 3B in rte_eth_(rxq|txq)_info.
> Unless in future will want to change it in struct rte_eth_dev_data too
> (or even hide it inside dev private queue data). 

I forgot about hairpin and bitmask... If so, I think it is
sufficient to fix absolutely misleading comment, say
that it is a bit mask and think about removal of
RTE_ETH_QUEUE_STATE_STOPPED (since it could be
stopped+hairpin). May be consider to use uin16_t,
since 8 bit is really small bitmask. It still fits in
available hole.