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

-----Original Message-----
From: Ferruh Yigit <redacted>
Sent: Thursday, 4 February 2021 2:13
To: Ido Goshen <redacted>
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:

quoted

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 <redacted>
---
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

+++++++++++++++++++++++++++++++++

quoted

  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 

quoted

+
  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);

quoted

  	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

quoted

+	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.

quoted

+	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?

quoted

+}
+
+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
  ############################################################################

quoted

+	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; }
+

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