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

["Wang, Haiyue" <haiyue.wang@intel.com>]

> -----Original Message-----
> From: Yigit, Ferruh
> Sent: Tuesday, September 10, 2019 23:00
> 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 12:41 PM, Wang, Haiyue wrote:
> >> -----Original Message-----
> >> From: Yigit, Ferruh
> >> Sent: Tuesday, September 10, 2019 17:15
> >> 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 9:37 AM, Wang, Haiyue wrote:
> >>>> -----Original Message-----
> >>>> From: Yigit, Ferruh
> >>>> Sent: Tuesday, September 10, 2019 16:07
> >>>> 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),
> >>>>
> >>>> 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 ?
> 

If I understand correctly, removed the unnecessary 'BURST_NORMAL' ?