mir/ovs
2
0
Fork 0
mirror of https://github.com/openvswitch/ovs synced 2025-08-31 14:25:26 +00:00
Code Issues Releases Wiki Activity

dpif-netdev: Detection and logging of suspicious PMD iterations

Browse Source 
This patch enhances dpif-netdev-perf to detect iterations with
suspicious statistics according to the following criteria:

- iteration lasts longer than US_THR microseconds (default 250).
  This can be used to capture events where a PMD is blocked or
  interrupted for such a period of time that there is a risk for
  dropped packets on any of its Rx queues.

- max vhost qlen exceeds a threshold Q_THR (default 128). This can
  be used to infer virtio queue overruns and dropped packets inside
  a VM, which are not visible in OVS otherwise.

Such suspicious iterations can be logged together with their iteration
statistics to be able to correlate them to packet drop or other events
outside OVS.

A new command is introduced to enable/disable logging at run-time and
to adjust the above thresholds for suspicious iterations:

ovs-appctl dpif-netdev/pmd-perf-log-set on | off
    [-b before] [-a after] [-e|-ne] [-us usec] [-q qlen]

Turn logging on or off at run-time (on|off).

-b before:  The number of iterations before the suspicious iteration to
            be logged (default 5).
-a after:   The number of iterations after the suspicious iteration to
            be logged (default 5).
-e:         Extend logging interval if another suspicious iteration is
            detected before logging occurs.
-ne:        Do not extend logging interval (default).
-q qlen:    Suspicious vhost queue fill level threshold. Increase this
            to 512 if the Qemu supports 1024 virtio queue length.
            (default 128).
-us usec:   change the duration threshold for a suspicious iteration
            (default 250 us).

Note: Logging of suspicious iterations itself consumes a considerable
amount of processing cycles of a PMD which may be visible in the iteration
history. In the worst case this can lead OVS to detect another
suspicious iteration caused by logging.

If more than 100 iterations around a suspicious iteration have been
logged once, OVS falls back to the safe default values (-b 5/-a 5/-ne)
to avoid that logging itself causes continuos further logging.

Signed-off-by: Jan Scheurich <jan.scheurich@ericsson.com>
Acked-by: Billy O'Mahony <billy.o.mahony@intel.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>
This commit is contained in:
Jan Scheurich
2018-04-19 19:40:46 +02:00
committed by Ian Stokes
parent 79f368756c
commit 7178fefbdf
5 changed files with 310 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
NEWS
View File

@@ -31,6 +31,8 @@ Post-v2.9.0
* Commands ovs-appctl dpif-netdev/pmd-*-show can now work on a single PMD
* Detailed PMD performance metrics available with new command
ovs-appctl dpif-netdev/pmd-perf-show
* Supervision of PMD performance metrics and logging of suspicious
iterations
v2.9.0 - 19 Feb 2018
--------------------

223
lib/dpif-netdev-perf.c
View File

@@ -25,6 +25,24 @@
VLOG_DEFINE_THIS_MODULE(pmd_perf);
#define ITER_US_THRESHOLD 250 /* Warning threshold for iteration duration
in microseconds. */
#define VHOST_QUEUE_FULL 128 /* Size of the virtio TX queue. */
#define LOG_IT_BEFORE 5 /* Number of iterations to log before
suspicious iteration. */
#define LOG_IT_AFTER 5 /* Number of iterations to log after
suspicious iteration. */
bool log_enabled = false;
bool log_extend = false;
static uint32_t log_it_before = LOG_IT_BEFORE;
static uint32_t log_it_after = LOG_IT_AFTER;
static uint32_t log_us_thr = ITER_US_THRESHOLD;
uint32_t log_q_thr = VHOST_QUEUE_FULL;
uint64_t iter_cycle_threshold;
static struct vlog_rate_limit latency_rl = VLOG_RATE_LIMIT_INIT(600, 600);
#ifdef DPDK_NETDEV
static uint64_t
get_tsc_hz(void)
@@ -141,6 +159,10 @@ pmd_perf_stats_init(struct pmd_perf_stats *s)
histogram_walls_set_log(&s->max_vhost_qfill, 0, 512);
s->iteration_cnt = 0;
s->start_ms = time_msec();
s->log_susp_it = UINT32_MAX;
s->log_begin_it = UINT32_MAX;
s->log_end_it = UINT32_MAX;
s->log_reason = NULL;
}
void
@@ -391,6 +413,10 @@ pmd_perf_stats_clear_lock(struct pmd_perf_stats *s)
history_init(&s->milliseconds);
s->start_ms = time_msec();
s->milliseconds.sample[0].timestamp = s->start_ms;
s->log_susp_it = UINT32_MAX;
s->log_begin_it = UINT32_MAX;
s->log_end_it = UINT32_MAX;
s->log_reason = NULL;
/* Clearing finished. */
s->clear = false;
ovs_mutex_unlock(&s->clear_mutex);
@@ -443,6 +469,7 @@ pmd_perf_end_iteration(struct pmd_perf_stats *s, int rx_packets,
uint64_t now_tsc = cycles_counter_update(s);
struct iter_stats *cum_ms;
uint64_t cycles, cycles_per_pkt = 0;
char *reason = NULL;
cycles = now_tsc - s->start_tsc;
s->current.timestamp = s->iteration_cnt;
@@ -492,9 +519,30 @@ pmd_perf_end_iteration(struct pmd_perf_stats *s, int rx_packets,
cum_ms->batches += s->current.batches;
cum_ms->max_vhost_qfill += s->current.max_vhost_qfill;
if (log_enabled) {
/* Log suspicious iterations. */
if (cycles > iter_cycle_threshold) {
reason = "Excessive total cycles";
} else if (s->current.max_vhost_qfill >= log_q_thr) {
reason = "Vhost RX queue full";
}
if (OVS_UNLIKELY(reason)) {
pmd_perf_set_log_susp_iteration(s, reason);
cycles_counter_update(s);
}
/* Log iteration interval around suspicious iteration when reaching
* the end of the range to be logged. */
if (OVS_UNLIKELY(s->log_end_it == s->iterations.idx)) {
pmd_perf_log_susp_iteration_neighborhood(s);
cycles_counter_update(s);
}
}
/* Store in iteration history. This advances the iteration idx and
* clears the next slot in the iteration history. */
history_store(&s->iterations, &s->current);
if (now_tsc > s->next_check_tsc) {
/* Check if ms is completed and store in milliseconds history. */
uint64_t now = time_msec();
@@ -515,3 +563,178 @@ pmd_perf_end_iteration(struct pmd_perf_stats *s, int rx_packets,
s->next_check_tsc = cycles_counter_update(s) + 10000;
}
}
/* Delay logging of the suspicious iteration and the range of iterations
* around it until after the last iteration in the range to be logged.
* This avoids any distortion of the measurements through the cost of
* logging itself. */
void
pmd_perf_set_log_susp_iteration(struct pmd_perf_stats *s,
char *reason)
{
if (s->log_susp_it == UINT32_MAX) {
/* No logging scheduled yet. */
s->log_susp_it = s->iterations.idx;
s->log_reason = reason;
s->log_begin_it = history_sub(s->iterations.idx, log_it_before);
s->log_end_it = history_add(s->iterations.idx, log_it_after + 1);
} else if (log_extend) {
/* Logging was initiated earlier, we log the previous suspicious
* iteration now and extend the logging interval, if possible. */
struct iter_stats *susp = &s->iterations.sample[s->log_susp_it];
uint32_t new_end_it, old_range, new_range;
VLOG_WARN_RL(&latency_rl,
"Suspicious iteration (%s): iter=%"PRIu64
" duration=%"PRIu64" us\n",
s->log_reason,
susp->timestamp,
(1000000L * susp->cycles) / get_tsc_hz());
new_end_it = history_add(s->iterations.idx, log_it_after + 1);
new_range = history_sub(new_end_it, s->log_begin_it);
old_range = history_sub(s->log_end_it, s->log_begin_it);
if (new_range < old_range) {
/* Extended range exceeds history length. */
new_end_it = s->log_begin_it;
}
s->log_susp_it = s->iterations.idx;
s->log_reason = reason;
s->log_end_it = new_end_it;
}
}
void
pmd_perf_log_susp_iteration_neighborhood(struct pmd_perf_stats *s)
{
ovs_assert(s->log_reason != NULL);
ovs_assert(s->log_susp_it != UINT32_MAX);
struct ds log = DS_EMPTY_INITIALIZER;
struct iter_stats *susp = &s->iterations.sample[s->log_susp_it];
uint32_t range = history_sub(s->log_end_it, s->log_begin_it);
VLOG_WARN_RL(&latency_rl,
"Suspicious iteration (%s): iter=%"PRIu64
" duration=%"PRIu64" us\n",
s->log_reason,
susp->timestamp,
(1000000L * susp->cycles) / get_tsc_hz());
pmd_perf_format_iteration_history(&log, s, range);
VLOG_WARN_RL(&latency_rl,
"Neighborhood of suspicious iteration:\n"
"%s", ds_cstr(&log));
ds_destroy(&log);
s->log_susp_it = s->log_end_it = s->log_begin_it = UINT32_MAX;
s->log_reason = NULL;
if (range > 100) {
/* Reset to safe default values to avoid disturbance. */
log_it_before = LOG_IT_BEFORE;
log_it_after = LOG_IT_AFTER;
log_extend = false;
}
}
void
pmd_perf_log_set_cmd(struct unixctl_conn *conn,
int argc, const char *argv[],
void *aux OVS_UNUSED)
{
unsigned int it_before, it_after, us_thr, q_thr;
bool on, extend;
bool usage = false;
on = log_enabled;
extend = log_extend;
it_before = log_it_before;
it_after = log_it_after;
q_thr = log_q_thr;
us_thr = log_us_thr;
while (argc > 1) {
if (!strcmp(argv[1], "on")) {
on = true;
argc--;
argv++;
} else if (!strcmp(argv[1], "off")) {
on = false;
argc--;
argv++;
} else if (!strcmp(argv[1], "-e")) {
extend = true;
argc--;
argv++;
} else if (!strcmp(argv[1], "-ne")) {
extend = false;
argc--;
argv++;
} else if (!strcmp(argv[1], "-a") && argc > 2) {
if (str_to_uint(argv[2], 10, &it_after)) {
if (it_after > HISTORY_LEN - 2) {
it_after = HISTORY_LEN - 2;
}
} else {
usage = true;
break;
}
argc -= 2;
argv += 2;
} else if (!strcmp(argv[1], "-b") && argc > 2) {
if (str_to_uint(argv[2], 10, &it_before)) {
if (it_before > HISTORY_LEN - 2) {
it_before = HISTORY_LEN - 2;
}
} else {
usage = true;
break;
}
argc -= 2;
argv += 2;
} else if (!strcmp(argv[1], "-q") && argc > 2) {
if (!str_to_uint(argv[2], 10, &q_thr)) {
usage = true;
break;
}
argc -= 2;
argv += 2;
} else if (!strcmp(argv[1], "-us") && argc > 2) {
if (!str_to_uint(argv[2], 10, &us_thr)) {
usage = true;
break;
}
argc -= 2;
argv += 2;
} else {
usage = true;
break;
}
}
if (it_before + it_after > HISTORY_LEN - 2) {
it_after = HISTORY_LEN - 2 - it_before;
}
if (usage) {
unixctl_command_reply_error(conn,
"Usage: ovs-appctl dpif-netdev/pmd-perf-log-set "
"[on|off] [-b before] [-a after] [-e|-ne] "
"[-us usec] [-q qlen]");
return;
}
VLOG_INFO("pmd-perf-log-set: %s, before=%d, after=%d, extend=%s, "
"us_thr=%d, q_thr=%d\n",
on ? "on" : "off", it_before, it_after,
extend ? "true" : "false", us_thr, q_thr);
log_enabled = on;
log_extend = extend;
log_it_before = it_before;
log_it_after = it_after;
log_q_thr = q_thr;
log_us_thr = us_thr;
iter_cycle_threshold = (log_us_thr * get_tsc_hz()) / 1000000L;
unixctl_command_reply(conn, "");
}

21
lib/dpif-netdev-perf.h
View File

@@ -175,6 +175,14 @@ struct pmd_perf_stats {
struct history iterations;
/* Millisecond history buffer. */
struct history milliseconds;
/* Suspicious iteration log. */
uint32_t log_susp_it;
/* Start of iteration range to log. */
uint32_t log_begin_it;
/* End of iteration range to log. */
uint32_t log_end_it;
/* Reason for logging suspicious iteration. */
char *log_reason;
};
/* Support for accurate timing of PMD execution on TSC clock cycle level.
@@ -350,6 +358,16 @@ history_store(struct history *h, struct iter_stats *is)
return history_next(h);
}
/* Data and function related to logging of suspicious iterations. */
extern bool log_enabled;
extern bool log_extend;
extern uint32_t log_q_thr;
extern uint64_t iter_cycle_threshold;
void pmd_perf_set_log_susp_iteration(struct pmd_perf_stats *s, char *reason);
void pmd_perf_log_susp_iteration_neighborhood(struct pmd_perf_stats *s);
/* Functions recording PMD metrics per iteration. */
void
@@ -375,6 +393,9 @@ void pmd_perf_format_iteration_history(struct ds *str,
int n_iter);
void pmd_perf_format_ms_history(struct ds *str, struct pmd_perf_stats *s,
int n_ms);
void pmd_perf_log_set_cmd(struct unixctl_conn *conn,
int argc, const char *argv[],
void *aux OVS_UNUSED);
#ifdef __cplusplus
}

59
lib/dpif-netdev-unixctl.man
View File

@@ -149,6 +149,65 @@ reported by the \fBdpif-netdev/pmd-stats-show\fR command.
To reset the counters and start a new measurement use
\fBdpif-netdev/pmd-stats-clear\fR.
.
.IP "\fBdpif-netdev/pmd-perf-log-set\fR \fBon\fR|\fBoff\fR \
[\fB-b\fR \fIbefore\fR] [\fB-a\fR \fIafter\fR] [\fB-e\fR|\fB-ne\fR] \
[\fB-us\fR \fIusec\fR] [\fB-q\fR \fIqlen\fR]"
.
The userspace "netdev" datapath is able to supervise the PMD performance
metrics and detect iterations with suspicious statistics according to the
following criteria:
.RS
.IP \(em
The iteration lasts longer than \fIusec\fR microseconds (default 250).
This can be used to capture events where a PMD is blocked or interrupted for
such a period of time that there is a risk for dropped packets on any of its Rx
queues.
.IP \(em
The max vhost qlen exceeds a threshold \fIqlen\fR (default 128). This can be
used to infer virtio queue overruns and dropped packets inside a VM, which are
not visible in OVS otherwise.
.RE
.IP
Such suspicious iterations can be logged together with their iteration
statistics in the \fBovs-vswitchd.log\fR to be able to correlate them to
packet drop or other events outside OVS.
The above command enables (\fBon\fR) or disables (\fBoff\fR) supervision and
logging at run-time and can be used to adjust the above thresholds for
detecting suspicious iterations. By default supervision and logging is
disabled.
The command options are:
.RS
.IP "\fB-b\fR \fIbefore\fR"
The number of iterations before the suspicious iteration to be logged
(default 5).
.IP "\fB-a\fR \fIafter\fR"
The number of iterations after the suspicious iteration to be logged
(default 5).
.IP "\fB-e\fR"
Extend logging interval if another suspicious iteration is detected
before logging occurs.
.IP "\fB-ne\fR"
Do not extend logging interval if another suspicious iteration is detected
before logging occurs (default).
.IP "\fB-q\fR \fIqlen\fR"
Suspicious vhost queue fill level threshold. Increase this to 512 if the Qemu
supports 1024 virtio queue length (default 128).
.IP "\fB-us\fR \fIusec\fR"
Change the duration threshold for a suspicious iteration (default 250 us).
.RE
Note: Logging of suspicious iterations itself consumes a considerable amount
of processing cycles of a PMD which may be visible in the iteration history.
In the worst case this can lead OVS to detect another suspicious iteration
caused by logging.
If more than 100 iterations around a suspicious iteration have been logged
once, OVS falls back to the safe default values (-b 5 -a 5 -ne) to avoid
that logging itself continuously causes logging of further suspicious
iterations.
.
.IP "\fBdpif-netdev/pmd-rxq-show\fR [\fB-pmd\fR \fIcore\fR] [\fIdp\fR]"
For one or all pmd threads of the datapath \fIdp\fR show the list of queue-ids
with port names, which this thread polls.

5
lib/dpif-netdev.c
View File

@@ -1235,6 +1235,11 @@ dpif_netdev_init(void)
unixctl_command_register("dpif-netdev/pmd-rxq-rebalance", "[dp]",
0, 1, dpif_netdev_pmd_rebalance,
NULL);
unixctl_command_register("dpif-netdev/pmd-perf-log-set",
"on|off [-b before] [-a after] [-e|-ne] "
"[-us usec] [-q qlen]",
0, 10, pmd_perf_log_set_cmd,
NULL);
return 0;
}