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

[Ferruh Yigit]

On 9/10/2019 12:41 PM, Wang, Haiyue wrote:
>> -----Original Message-----
>> From: Yigit, Ferruh
>> Sent: Tuesday, September 10, 2019 17:15
>> To: Wang, Haiyue <haiyue.wang at intel.com>; Richardson, Bruce <bruce.richardson at intel.com>
>> Cc: Ray Kinsella <mdr at ashroe.eu>; dev at dpdk.org; Sun, Chenmin <chenmin.sun at intel.com>
>> Subject: Re: [dpdk-dev] [RFC v2 1/3] ethdev: add the API for getting trace information
>>
>> On 9/10/2019 9:37 AM, Wang, Haiyue wrote:
>>>> -----Original Message-----
>>>> From: Yigit, Ferruh
>>>> Sent: Tuesday, September 10, 2019 16:07
>>>> To: Wang, Haiyue <haiyue.wang at intel.com>; Richardson, Bruce <bruce.richardson at intel.com>
>>>> Cc: Ray Kinsella <mdr at ashroe.eu>; dev at dpdk.org; Sun, Chenmin <chenmin.sun at 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 at intel.com>
>>>>>> Cc: Wang, Haiyue <haiyue.wang at intel.com>; Ray Kinsella <mdr at ashroe.eu>; dev at dpdk.org; Sun,
>> Chenmin
>>>>>> <chenmin.sun at 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 at ashroe.eu>; Wang, Haiyue <haiyue.wang at intel.com>
>>>>>>>>>>> Cc: dev at 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 at intel.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Enhance the PMD to support retrieving trace information like
>>>>>>>>>>>>>> Rx/Tx burst selection etc.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Signed-off-by: Haiyue Wang <haiyue.wang at 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),
>>>>
>>>> Do we need to have bitfields for this, I was suggesting reserve 4 bits, bit 2-5
>>>> (inclusive) and use their value:
>>>>
>>>> BURST_VECTOR_MODE_IDX  = 2
>>>> BURST_VECTOR_MODE_SIZE = 4
>>>> BURST_VECTOR_MODE_MASK =
>>>> 	((1 << BURST_VECTOR_MODE_SIZE) - 1) << BURST_VECTOR_MODE_IDX
>>>>
>>>> vector_mode = (options & BURST_VECTOR_MODE_MASK) >> BURST_VECTOR_MODE_IDX
>>>>
>>>> if (vector_mode == 0) // BURST_SSE
>>>> if (vector_mode == 1) // BURST_AVX2
>>>> if (vector_mode == 2) // BURST_AVX512
>>>> if (vector_mode == 3) // BURST_NEON
>>>> ....
>>>>
>>>> Can any vector mode be combination of above, if not why use bitfields?
>>>>
>>>
>>> I use it as this to *set* ...
>>>
>>> 	else if (pkt_burst == i40e_recv_scattered_pkts_vec_avx2)
>>> 		options = BURST_VECTOR | BURST_AVX2 | BURST_SCATTERED;
>>> 	else if (pkt_burst == i40e_recv_pkts_vec_avx2)
>>> 		options = BURST_VECTOR | BURST_AVX2;
>>> 	else if (pkt_burst == i40e_recv_scattered_pkts_vec)
>>> 		options = BURST_VECTOR | BURST_SSE | BURST_SCATTERED;
>>> 	else if (pkt_burst == i40e_recv_pkts_vec)
>>> 		options = BURST_VECTOR | BURST_SSE;
>>>
>>> Then *get* like this, since we reserve the bit group.
>>>
>>> static void
>>> burst_mode_options_display(uint64_t options)
>>> {
>>> 	uint64_t vec_mode = options & BURST_VECTOR_MODE_MASK;
>>> 	uint64_t opt;
>>>
>>> 	options &= ~BURST_VECTOR_MODE_MASK;
>>>
>>> 	for (opt = 1; options != 0; opt <<= 1, options >>= 1) {
>>> 		if (!(options & 1))
>>> 			continue;
>>>
>>> 		printf(" %s", rte_eth_burst_mode_option_name(opt));
>>>
>>> 		if (opt == BURST_VECTOR)
>>> 			printf("(%s)",
>>> 			       rte_eth_burst_mode_option_name(vec_mode));
>>> 	}
>>> }
>>>
>>
>> I can see how you intended use it, only they don't need to be bitfield and using
>> with value saves bits.
>> Also I think good to reserve some bits for future modes.
>>
> 
> "BURST_VECTOR_MODE_MASK = (0x3F << 2)" has reserved 63 non-zero bits on position 2 ~ 7.
> Then from bit 8, a new definition: BURST_SCATTERED = (1 << 8).
> 
> "using with value saves bits" -- Sorry, I didn't get the point. :-(
> vector_mode = (options & BURST_VECTOR_MODE_MASK) >> BURST_VECTOR_MODE_IDX
> 
> From above, 'vector_mode's bits are from 'options' bits stream, how to save bits ?
> In my understanding, this is some kind of more-bit-field, not each-bit-field.
> 
> I defined them together, so can quick check the vector type, like
> (options & BURST_VECTOR_MODE_MASK) == BURST_NEON.
> 
>>>>
>>>>>
>>>>> 	BURST_SCATTERED = (1 << 8),
>>>>> 	BURST_BULK_ALLOC = (1 << 9),
>>>>> 	BURST_NORMAL = (1 << 10),
>>>>
>>>> Not sure about this one, what is the difference between scalar?
>>>>
>>>
>>> Extract it from the function name and the debug message.
>>>
>>> 	if (pkt_burst == i40e_recv_scattered_pkts)
>>> 		options = BURST_SCALAR | BURST_SCATTERED;
>>> 	else if (pkt_burst == i40e_recv_pkts_bulk_alloc)
>>> 		options = BURST_SCALAR | BURST_BULK_ALLOC;
>>> 	else if (pkt_burst == i40e_recv_pkts)
>>> 		options = BURST_SCALAR | BURST_NORMAL;
>>
>> What is the difference between 'BURST_SCALAR' & "BURST_SCALAR | BURST_NORMAL" ?
> 
> IMO, "SCALAR" should be "non-Vector" ? Like "BURST_VECTOR" will append with
> "SSE/AVX2" etc, "SCALAR" will append with other option bits. "Normal" is just
> handing the Descriptor one by one as *normal*. As I said, I got this name idea
> from the original log to try cover the right burst behaviors. :)

Why using an additional flag to say there is not additional feature.
If mbuf bulk alloc supported it is: SCALAR | BULK_ALLOC
if scattered packets supported it is: SCALAR | SCATTERED
If no additional feature supported, why not just SCALAR ?

> 
>>
>> btw, for actual implementation please add 'RTE_ETH_' prefix.
>>
> Got it, will add them.
> 
>>>
>>>>> 	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;
>>>>> };
>>>>>
>>>>> And three APIs:
>>>>>
>>>>> 1.
>>>>> __rte_experimental
>>>>> int rte_eth_rx_burst_mode_get(uint16_t port_id, uint16_t queue_id,
>>>>> 	struct rte_eth_burst_mode *mode);
>>>>>
>>>>>
>>>>> 2.
>>>>> __rte_experimental
>>>>> int rte_eth_tx_burst_mode_get(uint16_t port_id, uint16_t queue_id,
>>>>> 	struct rte_eth_burst_mode *mode);
>>>>>
>>>>> 3.
>>>>> __rte_experimental
>>>>> const char *
>>>>> rte_eth_burst_mode_option_name(uint64_t option);
>>>>
>>>> What about 'rte_eth_burst_mode_name()' ?
>>>>
>>>
>>> The "mode" scope is bigger than "mode_option", so I defined it as "_mode_option_name()".
>>>
>>> struct rte_eth_burst_mode {
>>> 	uint32_t per_queue_support:1; /**< Support to set per queue burst */
>>>
>>> 	uint64_t options;
>>> };
>>
>> Agreed the scope is bigger in implementation, but "burst mode option name" is
>> same as "burst mode name" for user, so removing it may make easier for user.
>> But since the API is generating name from 'options' variable, instead of
>> directly from the port, OK to keep API name as you suggested.
>>
>>>
>>>>>
>>>>>
>>>>> PMD two ops:
>>>>>
>>>>> typedef void (*eth_burst_mode_get_t)(struct rte_eth_dev *dev,
>>>>> 	uint16_t queue_id, struct rte_eth_burst_mode *mode);
>>>>>
>>>>> struct eth_dev_ops {
>>>>> 	...
>>>>> 	eth_burst_mode_get_t       rx_burst_mode_get; /**< Get RX burst mode */
>>>>> 	eth_burst_mode_get_t       tx_burst_mode_get; /**< Get TX burst mode */
>>>>> 	...
>>>>> };
>>>>>
>>>
>