[ovs-dev] [PATCH v9 3/3] dpif-netdev: Detection and logging of suspicious PMD iterations

Stokes, Ian ian.stokes at intel.com
Fri Mar 16 11:11:16 UTC 2018


> -----Original Message-----
> From: Jan Scheurich [mailto:jan.scheurich at ericsson.com]
> Sent: Thursday, March 15, 2018 4:03 PM
> To: dev at openvswitch.org
> Cc: ktraynor at redhat.com; Stokes, Ian <ian.stokes at intel.com>;
> i.maximets at samsung.com; O Mahony, Billy <billy.o.mahony at intel.com>; Jan
> Scheurich <jan.scheurich at ericsson.com>
> Subject: [PATCH v9 3/3] dpif-netdev: Detection and logging of suspicious
> PMD iterations
> 
> 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 at ericsson.com>
> ---
>  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
>     - 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
> 43f537e..e6afd07 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;

Just a quick catch,

Compilation error: 
lib/dpif-netdev-perf.c:37:6: error: symbol 'log_extend' was not declared. Should it be static?

https://travis-ci.org/istokes/ovs/jobs/354225332

Thanks
Ian

> +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
> b91cb30..334908f 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 c4ac176..f059940
> 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;
>  }
> 
> --
> 1.9.1



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