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 23:07
> 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;
};