I see following behaviour:
1. Configure low -us (like 100)
2. After that I see many logs about suspicious iterations (expected).
2018-03-27T13:58:27Z|03574|pmd_perf(pmd7)|WARN|Suspicious iteration (Excessive
total cycles): tsc=520415762246435 duration=106 us
2018-03-27T13:58:27Z|03575|pmd_perf(pmd7)|WARN|Neighborhood of suspicious
iteration:
tsc cycles packets cycles/pkt pkts/batch
vhost qlen upcalls cycles/upcall
520415762297985 9711 32 303 32 424
0 0
520415762287041 10667 32 333 32 419
0 0
520415762277319 9722 32 303 32 429
0 0
520415762267083 9971 32 311 32 443
0 0
520415762257413 9670 32 302 32 451
0 0
520415762246435 10699 32 334 32 448
0 0
520415762235033 11109 32 347 32 455
0 0
520415762180220 9826 32 307 32 399
0 0
520415762169792 10229 32 319 32 413
0 0
520415762160385 9407 32 293 32 408
0 0
520415762150221 9891 32 309 32 434
0 0
2018-03-27T13:58:27Z|03576|pmd_perf(pmd7)|WARN|Suspicious iteration (Excessive
total cycles): tsc=520415762469997 duration=104 us
2018-03-27T13:58:27Z|03577|pmd_perf(pmd7)|WARN|Neighborhood of suspicious
iteration:
tsc cycles packets cycles/pkt pkts/batch
vhost qlen upcalls cycles/upcall
520415762519119 9462 32 295 32 505
0 0
520415762509595 9319 32 291 32 537
0 0
520415762500154 9283 32 290 32 569
0 0
520415762490585 9287 32 290 32 601
0 0
520415762480693 9730 32 304 32 633
0 0
520415762469997 10414 32 325 32 665
0 0
520415762459348 10342 32 323 32 697
0 0
520415762297985 9711 32 303 32 424
0 0
520415762287041 10667 32 333 32 419
0 0
520415762277319 9722 32 303 32 429
0 0
520415762267083 9971 32 311 32 443
0 0
3. Configure back high -us (like 1000).
4. Logs are still there with zero duration. Logs printed every second like this:
2018-03-27T14:02:08Z|04140|pmd_perf(pmd7)|WARN|Suspicious iteration (Excessive
total cycles): tsc=520437806368099 duration=0 us
[Thread 0x7fb56f2910 (LWP 19754) exited]
[New Thread 0x7fb56f2910 (LWP 19755)]
2018-03-27T14:02:08Z|04141|pmd_perf(pmd7)|WARN|Neighborhood of suspicious
iteration:
tsc cycles packets cycles/pkt pkts/batch
vhost qlen upcalls cycles/upcall
520437806368309 44 0 0 0 0
0 0
520437806368266 43 0 0 0 0
0 0
520437806368223 43 0 0 0 0
0 0
520437806368179 44 0 0 0 0
0 0
520437806368134 45 0 0 0 0
0 0
520437806368099 35 0 0 0 0
0 0
520437806005193 362819 0 0 0 0
0 0
520437806005149 44 0 0 0 0
0 0
520437806005105 44 0 0 0 0
0 0
520437806005061 44 0 0 0 0
0 0
520437806005017 44 0 0 0 0
0 0
2018-03-27T14:02:09Z|04142|pmd_perf(pmd7)|WARN|Suspicious iteration (Excessive
total cycles): tsc=520437909369235 duration=0 us
[Thread 0x7fb56f2910 (LWP 19755) exited]
[New Thread 0x7fb56f2910 (LWP 19756)]
2018-03-27T14:02:09Z|04143|pmd_perf(pmd7)|WARN|Neighborhood of suspicious
iteration:
tsc cycles packets cycles/pkt pkts/batch
vhost qlen upcalls cycles/upcall
520437909369437 44 0 0 0 0
0 0
520437909369393 44 0 0 0 0
0 0
520437909369350 43 0 0 0 0
0 0
520437909369306 44 0 0 0 0
0 0
520437909369262 44 0 0 0 0
0 0
520437909369235 27 0 0 0 0
0 0
520437909006124 362999 0 0 0 0
0 0
520437909006080 44 0 0 0 0
0 0
520437909006035 45 0 0 0 0
0 0
520437909005991 44 0 0 0 0
0 0
520437909005947 44 0 0 0 0
0 0
5. Logs could be stopped only by setting -us to extremely high value like 10000.
Is it expected?
One more comment inline.
On 18.03.2018 20:55, Jan Scheurich wrote:
> 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 <[email protected]>
> Acked-by: Billy O'Mahony <[email protected]>
> ---
> NEWS | 2 +
> lib/dpif-netdev-perf.c | 201
> ++++++++++++++++++++++++++++++++++++++++++++
> lib/dpif-netdev-perf.h | 42 +++++++++
> lib/dpif-netdev-unixctl.man | 59 +++++++++++++
> lib/dpif-netdev.c | 5 ++
> 5 files changed, 309 insertions(+)
>
> diff --git a/NEWS b/NEWS
> index 8f66fd3..61148b1 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -76,6 +76,8 @@ v2.9.0 - 19 Feb 2018
> * 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
Same Post-v2.9.0.
> - vswitchd:
> * Datapath IDs may now be specified as 0x1 (etc.) instead of 16 digits.
> * Configuring a controller, or unconfiguring all controllers, now
> deletes
> diff --git a/lib/dpif-netdev-perf.c b/lib/dpif-netdev-perf.c
> index 2b36410..410a209 100644
> --- a/lib/dpif-netdev-perf.c
> +++ b/lib/dpif-netdev-perf.c
> @@ -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)
> @@ -127,6 +145,10 @@ pmd_perf_stats_init(struct pmd_perf_stats *s)
> histogram_walls_set_log(&s->cycles_per_upcall, 1000, 1000000);
> histogram_walls_set_log(&s->max_vhost_qfill, 0, 512);
> 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
> @@ -382,6 +404,10 @@ 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);
> @@ -402,3 +428,178 @@ pmd_perf_stats_clear(struct pmd_perf_stats *s)
> s->clear = true;
> }
> }
> +
> +/* 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 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): tsc=%"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): tsc=%"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, "");
> +}
> diff --git a/lib/dpif-netdev-perf.h b/lib/dpif-netdev-perf.h
> index fd9b0fc..985aa5a 100644
> --- a/lib/dpif-netdev-perf.h
> +++ b/lib/dpif-netdev-perf.h
> @@ -171,6 +171,14 @@ 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.
> @@ -341,6 +349,15 @@ 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 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. */
>
> static inline void
> @@ -370,6 +387,7 @@ 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->current.timestamp;
> s->current.cycles = cycles;
> @@ -421,6 +439,27 @@ pmd_perf_end_iteration(struct pmd_perf_stats *s, int
> rx_packets,
> /* 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 (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);
> + }
> + }
> +
> if (now_tsc > s->next_check_tsc) {
> /* Check if ms is completed and store in milliseconds history. */
> uint64_t now = time_msec();
> @@ -458,6 +497,9 @@ 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
> }
> diff --git a/lib/dpif-netdev-unixctl.man b/lib/dpif-netdev-unixctl.man
> index 76c3e4e..ab8619e 100644
> --- a/lib/dpif-netdev-unixctl.man
> +++ b/lib/dpif-netdev-unixctl.man
> @@ -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.
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index f245ce2..670e5c1 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -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;
> }
>
>
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