Re: [dpdk-dev] [PATCH v3 1/1] net/pcap: imissed stats support

[Ido Goshen <Ido@cgstowernetworks.com>]

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Thursday, 4 February 2021 2:13
> To: Ido Goshen <Ido@cgstowernetworks.com>
> Cc: dev@dpdk.org
> Subject: Re: [PATCH v3 1/1] net/pcap: imissed stats support
> 
> On 2/3/2021 11:07 PM, Ido Goshen wrote:
> > get value from pcap_stats.ps_drop (see man pcap_stats) the value is
> > adjusted in this cases:
> >   - port stop - pcap is closed and will lose count
> >   - stats reset - pcap doesn't provide reset api
> >   - rollover - pcap counter size is u_32 only
> >
> > Signed-off-by: Ido Goshen <ido@cgstowernetworks.com>
> > ---
> > v3:
> > * code cleanup by dedicated struct and functions extraction
> > * multi stop support by menmonic+= accumulation
> > * rollover fixup
> >
> > v2:
> > * sum all queues (rx_missed_total += fix)
> > * null pcap protection
> > * inter stop/start persistancy (counter won't reset on stop)
> >
> >   drivers/net/pcap/rte_eth_pcap.c | 59
> +++++++++++++++++++++++++++++++++
> >   1 file changed, 59 insertions(+)
> >
> > diff --git a/drivers/net/pcap/rte_eth_pcap.c
> > b/drivers/net/pcap/rte_eth_pcap.c index a32b1f3f3..16e8752f3 100644
> > --- a/drivers/net/pcap/rte_eth_pcap.c
> > +++ b/drivers/net/pcap/rte_eth_pcap.c
> > @@ -60,11 +60,21 @@ struct queue_stat {
> >   	volatile unsigned long err_pkts;
> >   };
> >
> > +struct queue_missed_stat {
> > +	/* last value retrieved from pcap */
> > +	volatile unsigned int pcap;
> > +	/* stores values lost by pcap stop or rollover */
> > +	volatile unsigned long mnemonic;
> > +	/* value on last reset */
> > +	volatile unsigned long reset;
> > +};
> 
> I am aware other stats has 'volatile' keyword, but as far as I can see it is not
> needed, since these are new ones can you please drop the 'volatile'?

ok 

> 
> > +
> >   struct pcap_rx_queue {
> >   	uint16_t port_id;
> >   	uint16_t queue_id;
> >   	struct rte_mempool *mb_pool;
> >   	struct queue_stat rx_stat;
> > +	struct queue_missed_stat missed_stat;
> >   	char name[PATH_MAX];
> >   	char type[ETH_PCAP_ARG_MAXLEN];
> >
> > @@ -144,6 +154,49 @@ RTE_LOG_REGISTER(eth_pcap_logtype,
> pmd.net.pcap, NOTICE);
> >   	rte_log(RTE_LOG_ ## level, eth_pcap_logtype, \
> >   		"%s(): " fmt "\n", __func__, ##args)
> >
> > +static struct queue_missed_stat*
> > +queue_missed_stat_update(struct rte_eth_dev *dev, unsigned int qid) {
> > +	struct pmd_internals *internals = dev->data->dev_private;
> > +	struct queue_missed_stat *missed_stat =
> > +			&internals->rx_queue[qid].missed_stat;
> > +	const struct pmd_process_private *pp = dev->process_private;
> > +	pcap_t *pcap = pp->rx_pcap[qid];
> > +	struct pcap_stat stat;
> 
> Can you please put an empty line after variable declarations, and before return.

ok

> 
> > +	if (!pcap || (pcap_stats(pcap, &stat) != 0))
> > +		return missed_stat;
> > +	/* rollover check - best effort fixup assuming single rollover */
> > +	if (stat.ps_drop < missed_stat->pcap)
> > +		missed_stat->mnemonic += UINT_MAX;
> > +	missed_stat->pcap = stat.ps_drop;
> 
> here.
> 
> > +	return missed_stat;
> > +}
> > +
> > +static void
> > +queue_missed_stat_on_stop_update(struct rte_eth_dev *dev, unsigned
> > +int qid) {
> > +	struct queue_missed_stat *missed_stat =
> > +			queue_missed_stat_update(dev, qid);
> > +	missed_stat->mnemonic += missed_stat->pcap;
> 
> Better to reset 'missed_stat->pcap' afterwards, in case stats requested before
> port started again:
>   missed_stat->pcap = 0;

right, should be careful not to double count it
but maybe better to set it to 0 in queue_missed_stat_update in the stop return case
	if (!pcap || (pcap_stats(pcap, &stat) != 0))
	{
		missed_stat->pcap = 0;
		return missed_stat;
	}
this way the missed_stat->pcap will always represent the current value from pcap and not hold old value
specifically in case port is stopped it will be 0 and not re-added 
agree?

> 
> > +}
> > +
> > +static void
> > +queue_missed_stat_reset(struct rte_eth_dev *dev, unsigned int qid) {
> > +	struct queue_missed_stat *missed_stat =
> > +			queue_missed_stat_update(dev, qid);
> > +	missed_stat->reset = missed_stat->pcap;
> 
> I guess this should be:
> "missed_stat->reset = missed_stat->pcap + missed_stat->mnemonic;"

I don't think so
reset should only remember where pcap was at the reset point and not store old values
trying it immediately results in

testpmd> show port stats 0

  ######################## NIC statistics for port 0  ########################
  RX-packets: 0          RX-missed: 1940       RX-bytes:  0
  RX-errors: 0
  RX-nombuf:  0         
  TX-packets: 0          TX-errors: 0          TX-bytes:  0

  Throughput (since last show)
  Rx-pps:            0          Rx-bps:            0
  Tx-pps:            0          Tx-bps:            0
  ############################################################################
testpmd> clear port stats 0

  NIC statistics for port 0 cleared
testpmd> show port stats 0

  ######################## NIC statistics for port 0  ########################
  RX-packets: 0          RX-missed: 18446744073709550646 RX-bytes:  0
  RX-errors: 0
  RX-nombuf:  0         
  TX-packets: 0          TX-errors: 0          TX-bytes:  0

  Throughput (since last show)
  Rx-pps:            0          Rx-bps:            0
  Tx-pps:            0          Tx-bps:            0
  ############################################################################

> > +	missed_stat->mnemonic = 0;
> > +}
> > +
> > +static unsigned long
> > +queue_missed_stat_get(struct rte_eth_dev *dev, unsigned int qid) {
> > +	const struct queue_missed_stat *missed_stat =
> > +			queue_missed_stat_update(dev, qid);
> > +	return missed_stat->pcap + missed_stat->mnemonic -
> > +missed_stat->reset; }
> > +
> 
> <...>