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dpif-netdev: Refactor cycle counting

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Simplify the historically grown TSC cycle counting in PMD threads.
Cycles are currently counted for the following purposes:

1. Measure PMD ustilization

PMD utilization is defined as ratio of cycles spent in busy iterations
(at least one packet received or sent) over the total number of cycles.

This is already done in pmd_perf_start_iteration() and
pmd_perf_end_iteration() based on a TSC timestamp saved in current
iteration at start_iteration() and the actual TSC at end_iteration().
No dependency on intermediate cycle accounting.

2. Measure the processing load per RX queue

This comprises cycles spend on polling and processing packets received
from the rx queue and the cycles spent on delayed sending of these packets
to tx queues (with time-based batching).

The previous scheme using cycles_count_start(), cycles_count_intermediate()
and cycles-count_end() originally introduced to simplify cycle counting
and saving calls to rte_get_tsc_cycles() was rather obscuring things.

Replace by a nestable cycle_timer with with start and stop functions to
embrace a code segment to be timed. The timed code may contain arbitrary
nested cycle_timers. The duration of nested timers is excluded from the
outer timer.

The caller must ensure that each call to cycle_timer_start() is
followed by a call to cycle_timer_end(). Failure to do so will lead to
assertion failure or a memory leak.

The new cycle_timer is used to measure the processing cycles per rx queue.
This is not yet strictly necessary but will be made use of in a subsequent
commit.

All cycle count functions and data are relocated to module
dpif-netdev-perf.

Signed-off-by: Jan Scheurich <jan.scheurich@ericsson.com>
Acked-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Billy O'Mahony <billy.o.mahony@intel.com>
Signed-off: Ian Stokes <ian.stokes@intel.com>
This commit is contained in:
Jan Scheurich
2018-01-15 12:27:24 +01:00
committed by Ian Stokes
parent 82a48ead4e
commit a19896abe5
2 changed files with 135 additions and 95 deletions
Download Patch File Download Diff File Expand all files Collapse all files

120
lib/dpif-netdev.c
View File

@@ -32,10 +32,6 @@
#include <sys/stat.h>
#include <unistd.h>
#ifdef DPDK_NETDEV
#include <rte_cycles.h>
#endif
#include "bitmap.h"
#include "cmap.h"
#include "conntrack.h"
@@ -509,8 +505,6 @@ struct tx_port {
struct dp_netdev_pmd_thread_ctx {
/* Latest measured time. See 'pmd_thread_ctx_time_update()'. */
long long now;
/* Used to count cycles. See 'cycles_count_end()' */
unsigned long long last_cycles;
};
/* PMD: Poll modes drivers. PMD accesses devices via polling to eliminate
@@ -3111,58 +3105,6 @@ dp_netdev_actions_free(struct dp_netdev_actions *actions)
free(actions);
}
static inline unsigned long long
cycles_counter(void)
{
#ifdef DPDK_NETDEV
return rte_get_tsc_cycles();
#else
return 0;
#endif
}
/* Fake mutex to make sure that the calls to cycles_count_* are balanced */
extern struct ovs_mutex cycles_counter_fake_mutex;
/* Start counting cycles. Must be followed by 'cycles_count_end()' */
static inline void
cycles_count_start(struct dp_netdev_pmd_thread *pmd)
OVS_ACQUIRES(&cycles_counter_fake_mutex)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
pmd->ctx.last_cycles = cycles_counter();
}
/* Stop counting cycles and add them to the counter 'type' */
static inline void
cycles_count_end(struct dp_netdev_pmd_thread *pmd,
enum pmd_stat_type type)
OVS_RELEASES(&cycles_counter_fake_mutex)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
unsigned long long interval = cycles_counter() - pmd->ctx.last_cycles;
pmd_perf_update_counter(&pmd->perf_stats, type, interval);
}
/* Calculate the intermediate cycle result and add to the counter 'type' */
static inline void
cycles_count_intermediate(struct dp_netdev_pmd_thread *pmd,
struct dp_netdev_rxq *rxq,
enum pmd_stat_type type)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
unsigned long long new_cycles = cycles_counter();
unsigned long long interval = new_cycles - pmd->ctx.last_cycles;
pmd->ctx.last_cycles = new_cycles;
pmd_perf_update_counter(&pmd->perf_stats, type, interval);
if (rxq && (type == PMD_CYCLES_POLL_BUSY)) {
/* Add to the amount of current processing cycles. */
non_atomic_ullong_add(&rxq->cycles[RXQ_CYCLES_PROC_CURR], interval);
}
}
static void
dp_netdev_rxq_set_cycles(struct dp_netdev_rxq *rx,
enum rxq_cycles_counter_type type,
@@ -3171,6 +3113,14 @@ dp_netdev_rxq_set_cycles(struct dp_netdev_rxq *rx,
atomic_store_relaxed(&rx->cycles[type], cycles);
}
static void
dp_netdev_rxq_add_cycles(struct dp_netdev_rxq *rx,
enum rxq_cycles_counter_type type,
unsigned long long cycles)
{
non_atomic_ullong_add(&rx->cycles[type], cycles);
}
static uint64_t
dp_netdev_rxq_get_cycles(struct dp_netdev_rxq *rx,
enum rxq_cycles_counter_type type)
@@ -3234,27 +3184,40 @@ dp_netdev_pmd_flush_output_packets(struct dp_netdev_pmd_thread *pmd)
static int
dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread *pmd,
struct netdev_rxq *rx,
struct dp_netdev_rxq *rxq,
odp_port_t port_no)
{
struct dp_packet_batch batch;
struct cycle_timer timer;
int error;
int batch_cnt = 0;
/* Measure duration for polling and processing rx burst. */
cycle_timer_start(&pmd->perf_stats, &timer);
dp_packet_batch_init(&batch);
error = netdev_rxq_recv(rx, &batch);
error = netdev_rxq_recv(rxq->rx, &batch);
if (!error) {
/* At least one packet received. */
*recirc_depth_get() = 0;
pmd_thread_ctx_time_update(pmd);
batch_cnt = batch.count;
dp_netdev_input(pmd, &batch, port_no);
dp_netdev_pmd_flush_output_packets(pmd);
} else if (error != EAGAIN && error != EOPNOTSUPP) {
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
VLOG_ERR_RL(&rl, "error receiving data from %s: %s",
netdev_rxq_get_name(rx), ovs_strerror(error));
/* Assign processing cycles to rx queue. */
uint64_t cycles = cycle_timer_stop(&pmd->perf_stats, &timer);
dp_netdev_rxq_add_cycles(rxq, RXQ_CYCLES_PROC_CURR, cycles);
} else {
/* Discard cycles. */
cycle_timer_stop(&pmd->perf_stats, &timer);
if (error != EAGAIN && error != EOPNOTSUPP) {
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
VLOG_ERR_RL(&rl, "error receiving data from %s: %s",
netdev_rxq_get_name(rxq->rx), ovs_strerror(error));
}
}
return batch_cnt;
@@ -3880,30 +3843,22 @@ dpif_netdev_run(struct dpif *dpif)
struct dp_netdev *dp = get_dp_netdev(dpif);
struct dp_netdev_pmd_thread *non_pmd;
uint64_t new_tnl_seq;
int process_packets = 0;
ovs_mutex_lock(&dp->port_mutex);
non_pmd = dp_netdev_get_pmd(dp, NON_PMD_CORE_ID);
if (non_pmd) {
ovs_mutex_lock(&dp->non_pmd_mutex);
cycles_count_start(non_pmd);
HMAP_FOR_EACH (port, node, &dp->ports) {
if (!netdev_is_pmd(port->netdev)) {
int i;
for (i = 0; i < port->n_rxq; i++) {
process_packets =
dp_netdev_process_rxq_port(non_pmd,
port->rxqs[i].rx,
port->port_no);
cycles_count_intermediate(non_pmd, NULL,
process_packets
? PMD_CYCLES_POLL_BUSY
: PMD_CYCLES_POLL_IDLE);
dp_netdev_process_rxq_port(non_pmd,
&port->rxqs[i],
port->port_no);
}
}
}
cycles_count_end(non_pmd, PMD_CYCLES_POLL_IDLE);
pmd_thread_ctx_time_update(non_pmd);
dpif_netdev_xps_revalidate_pmd(non_pmd, false);
ovs_mutex_unlock(&dp->non_pmd_mutex);
@@ -4082,18 +4037,14 @@ reload:
lc = UINT_MAX;
}
cycles_count_start(pmd);
cycles_counter_update(s);
for (;;) {
uint64_t iter_packets = 0;
pmd_perf_start_iteration(s, pmd->ctx.last_cycles);
pmd_perf_start_iteration(s);
for (i = 0; i < poll_cnt; i++) {
process_packets =
dp_netdev_process_rxq_port(pmd, poll_list[i].rxq->rx,
dp_netdev_process_rxq_port(pmd, poll_list[i].rxq,
poll_list[i].port_no);
cycles_count_intermediate(pmd, poll_list[i].rxq,
process_packets
? PMD_CYCLES_POLL_BUSY
: PMD_CYCLES_POLL_IDLE);
iter_packets += process_packets;
}
@@ -4115,13 +4066,10 @@ reload:
if (reload) {
break;
}
cycles_count_intermediate(pmd, NULL, PMD_CYCLES_OVERHEAD);
}
pmd_perf_end_iteration(s, pmd->ctx.last_cycles, iter_packets);
pmd_perf_end_iteration(s, iter_packets);
}
cycles_count_end(pmd, PMD_CYCLES_OVERHEAD);
poll_cnt = pmd_load_queues_and_ports(pmd, &poll_list);
exiting = latch_is_set(&pmd->exit_latch);
/* Signal here to make sure the pmd finishes