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

[Wang, Haiyue]

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),

	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;
};

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);


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 */
	...
};