Re: [dpdk-dev] [RFC v2 1/3] ethdev: add the API for getting trace information

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 9/10/2019 4:21 PM, Wang, Haiyue wrote:
>> -----Original Message-----
>> From: Yigit, Ferruh
>> Sent: Tuesday, September 10, 2019 23:07
>> To: Wang, Haiyue <haiyue.wang@intel.com>; Richardson, Bruce <bruce.richardson@intel.com>
>> Cc: Ray Kinsella <mdr@ashroe.eu>; dev@dpdk.org; Sun, Chenmin <chenmin.sun@intel.com>
>> Subject: Re: [dpdk-dev] [RFC v2 1/3] ethdev: add the API for getting trace information
>>
>> On 9/10/2019 5:36 AM, Wang, Haiyue wrote:
>>> Thanks Ferruh, Bruce.
>>>
>>>> -----Original Message-----
>>>> From: Yigit, Ferruh
>>>> Sent: Monday, September 9, 2019 21:18
>>>> To: Richardson, Bruce <bruce.richardson@intel.com>
>>>> Cc: Wang, Haiyue <haiyue.wang@intel.com>; Ray Kinsella <mdr@ashroe.eu>; dev@dpdk.org; Sun, Chenmin
>>>> <chenmin.sun@intel.com>
>>>> Subject: Re: [dpdk-dev] [RFC v2 1/3] ethdev: add the API for getting trace information
>>>>
>>>> On 9/9/2019 1:50 PM, Ferruh Yigit wrote:
>>>>> On 9/9/2019 1:40 PM, Bruce Richardson wrote:
>>>>>> On Mon, Sep 09, 2019 at 12:23:36PM +0100, Ferruh Yigit wrote:
>>>>>>> On 9/7/2019 3:42 AM, Wang, Haiyue wrote:
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: Yigit, Ferruh
>>>>>>>>> Sent: Friday, September 6, 2019 22:22
>>>>>>>>> To: Ray Kinsella <mdr@ashroe.eu>; Wang, Haiyue <haiyue.wang@intel.com>
>>>>>>>>> Cc: dev@dpdk.org
>>>>>>>>> Subject: Re: [dpdk-dev] [RFC v2 1/3] ethdev: add the API for getting trace information
>>>>>>>>>
>>>>>>>>> On 8/13/2019 1:51 PM, Ray Kinsella wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 13/08/2019 04:24, Stephen Hemminger wrote:
>>>>>>>>>>> On Tue, 13 Aug 2019 11:06:10 +0800
>>>>>>>>>>> Haiyue Wang <haiyue.wang@intel.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Enhance the PMD to support retrieving trace information like
>>>>>>>>>>>> Rx/Tx burst selection etc.
>>>>>>>>>>>>
>>>>>>>>>>>> Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
>>>>>>>>>>>> ---
>>>>>>>>>>>>  lib/librte_ethdev/rte_ethdev.c      | 18 ++++++++++++++++++
>>>>>>>>>>>>  lib/librte_ethdev/rte_ethdev.h      |  9 +++++++++
>>>>>>>>>>>>  lib/librte_ethdev/rte_ethdev_core.h |  4 ++++
>>>>>>>>>>>>  3 files changed, 31 insertions(+)
>>>>>>>>>>>>
>>>>>>>>>>>> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
>>>>>>>>>>>> index 17d183e..6098fad 100644
>>>>>>>>>>>> --- a/lib/librte_ethdev/rte_ethdev.c
>>>>>>>>>>>> +++ b/lib/librte_ethdev/rte_ethdev.c
>>>>>>>>>>>> @@ -4083,6 +4083,24 @@ rte_eth_tx_queue_info_get(uint16_t port_id, uint16_t queue_id,
>>>>>>>>>>>>  }
>>>>>>>>>>>>
>>>>>>>>>>>>  int
>>>>>>>>>>>> +rte_eth_trace_info_get(uint16_t port_id, uint16_t queue_id,
>>>>>>>>>>>> +		       enum rte_eth_trace type, char *buf, int sz)
>>>>>>>>>
>>>>>>>>> Better to use struct as argument instead of individual variables because it is
>>>>>>>>> easier to extend the struct later if needed.
>>>>>>>>>
>>>>>>>>>>>> +{
>>>>>>>>>>>> +	struct rte_eth_dev *dev;
>>>>>>>>>>>> +
>>>>>>>>>>>> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
>>>>>>>>>>>> +
>>>>>>>>>>>> +	if (buf == NULL)
>>>>>>>>>>>> +		return -EINVAL;
>>>>>>>>>>>> +
>>>>>>>>>>>> +	dev = &rte_eth_devices[port_id];
>>>>>>>>>>>> +
>>>>>>>>>>>> +	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->trace_info_get, -ENOTSUP);
>>>>>>>>>>>> +
>>>>>>>>>>>> +	return dev->dev_ops->trace_info_get(dev, queue_id, type, buf, sz);
>>>>>>>>>>>
>>>>>>>>>>> What if queueid is out of bounds?
>>>>>>>>>>>
>>>>>>>>>>> The bigger problem is that this information is like a log message
>>>>>>>>>>> and unstructured, which makes it device specific and useless for automation.
>>>>>>>>>>
>>>>>>>>>> IMHO - this is much better implemented as a capability bitfield, that
>>>>>>>>>> can be queried.
>>>>>>>>>
>>>>>>>>> +1 to return the datapath capability as bitfield.
>>>>>>>>>
>>>>>>>>> Also +1 to have a new API,
>>>>>>>>> - I am not sure about the API name, 'rte_eth_trace_info_get()', can we find
>>>>>>>>> something better instead of 'trace' there.
>>>>>>>>> - I think we should limit this API only to get current datapath configuration,
>>>>>>>>> for clarity of the API don't return capability or not datapath related config.
>>>>>>>>>
>>>>>>>>> Also this information not always supported in queue level, what do you think
>>>>>>>>> having ability to get this information in port level,
>>>>>>>>> like this API can return a struct, which may have a field that says if the
>>>>>>>>> output is for queue or port, or this can be another bitfield, what do you think?
>>>>>>>>>
>>>>>>>>
>>>>>>>> #define RX_SCALAR	(1ULL < 0)
>>>>>>>> #define RX_VECTOR_AVX2  ...
>>>>>>>
>>>>>>> What about having RX_VECTOR value, later another bit group for the details of
>>>>>>> the vectorization:
>>>>>>> SSE
>>>>>>> AVX2
>>>>>>> AVX512
>>>>>>> NEON
>>>>>>> ALTIVEC
>>>>>>>
>>>>>>> Since above options can exist together, what about using values for them instead
>>>>>>> of bitfields? Reserving 4 bits, 2^4 = 16, can be enough I think for long term.
>>>>>>>
>>>>>> Rather than having named vector types, we just need to worry about the ones
>>>>>> for the current architecture. Therefore I'd suggest just using vector
>>>>>> widths, one bit each for 16B, 32B and 64B vector support. For supporting
>>>>>> multiple values, 16 combinations is not enough for all the possibilities.
>>>>>>
>>>>>
>>>>> vector width can be an option too, no objection there. But this is only for
>>>>> current configuration, so it can be a combination, we have now 5 types and
>>>>> allocating space for 16.
>>>>>
>>>>
>>>> correction: it can *not* be a combination
>>>
>>> I think we can merge the RX_VECTOR and TX_VECTOR together, use 6 bits for vector
>>> mode detail. And for vector width, the SSE, NEON name should indicates it ?
>>>
>>> I renamed the definitions to try to make things clear.
>>>
>>> enum rte_eth_burst_mode_option {
>>> 	BURST_SCALAR = (1 << 0),
>>> 	BURST_VECTOR = (1 << 1),
>>>
>>> 	BURST_VECTOR_MODE_MASK = (0x3F << 2),
>>> 	BURST_ALTIVEC          = (1 << 2),
>>> 	BURST_NEON             = (2 << 2),
>>> 	BURST_SSE              = (3 << 2),
>>> 	BURST_AVX2             = (4 << 2),
>>> 	BURST_AVX512           = (5 << 2),
>>>
>>> 	BURST_SCATTERED = (1 << 8),
>>> 	BURST_BULK_ALLOC = (1 << 9),
>>> 	BURST_NORMAL = (1 << 10),
>>> 	BURST_SIMPLE = (1 << 11),
>>> };
>>>
>>> /**
>>>  * Ethernet device RX/TX queue packet burst mode information structure.
>>>  * Used to retrieve information about packet burst mode setting.
>>>  */
>>> struct rte_eth_burst_mode {
>>> 	uint32_t per_queue_support:1; /**< Support to set per queue burst */
>>>
>>> 	uint64_t options;
>>
>> We are using first 32bits just to detect the queue level support, what do you
>> think converting this into a field in 'rte_eth_burst_mode_option' and use
>> 'options' fields, so we will fit into 64 bit.
> 
> Yes, it's clear.
> Then do we still use 'struct rte_eth_burst_mode' to hold one member "uint64_t options" ?
> 
> struct rte_eth_burst_mode {
> 	uint64_t options;
> };
> 

I suggest keeping the struct, for the possibility of future changes.