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: 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  ...
...
#define RX_SCATTER ...
#define RX_BULK_ALLOC
#define TX_SCALAR
#define TX_VECTOR_AVX2 ..
...
#define TX_SIMPLE

struct rte_pkt_burst_info {
	bool per_queue_support; /* Per queue has each rx/tx burst setting */
	uint64_t burst_infos;
};

int
rte_eth_pkt_burst_info_get(uint16_t port_id, bool is_rx, uint16_t queue_id,
		       	struct rte_pkt_burst_info *pbinfo)

Rx/Tx shares the 64 bits definition, but return according to 'is_rx'.
Application can call with 'queue_id = 0' firstly, if the Rx/Tx queue
support queue level burst setting, then 'per_queue_support = true', then
it can iterate to get the burst info with different 'queue_id', of course,
the 'per_queue_support = true' will be returned always.

How about this ?


> >
> >>
> >> Why not just keep it in the log like it is now?
> >>
> >>>  int rte_eth_tx_queue_info_get(uint16_t port_id, uint16_t queue_id,
> >>>  	struct rte_eth_txq_info *qinfo);
> >>>
> >>> +int
> >>> +rte_eth_trace_info_get(uint16_t port_id, uint16_t queue_id,
> >>> +	enum rte_eth_trace type, char *buf, int sz);
> >>> +
> >>
> >> You didn't run checkpatch, otherwise you would have seen complaints
> >> about not listing API as experimental.
> >>
> >> Also the API would have to be in the map file as well.
> >>
> >> Docbook comments are also missing.
> >>
> >>
> >>
> >>