[ovs-dev,v3,3/3] dpif-netdev: Detection and logging of suspicious PMD

Message ID CFF8EF42F1132E4CBE2BF0AB6C21C58D8CECD226@ESESSMB107.ericsson.se
State New
Delegated to: Ian Stokes
Headers show
Series
  • Untitled series #14487
Related show

Commit Message

Jan Scheurich Nov. 21, 2017, 12:38 a.m.
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] [-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).
-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).

If more than 100 iterations before or after a suspicious iteration have
been looged once, OVS falls back to the safe default values (5/5) to
avoid that logging itself causes continuos further logging.

Signed-off-by: Jan Scheurich <jan.scheurich@ericsson.com>
---
 lib/dpif-netdev-perf.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++++
 lib/dpif-netdev-perf.h |  32 +++++++++++
 lib/dpif-netdev.c      |   5 ++
 3 files changed, 178 insertions(+)

Patch

diff --git a/lib/dpif-netdev-perf.c b/lib/dpif-netdev-perf.c
index 42d93a2..455c4b5 100644
--- a/lib/dpif-netdev-perf.c
+++ b/lib/dpif-netdev-perf.c
@@ -28,6 +28,23 @@ 
 
 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 iteration to log before
+                                   suspicious iteration. */
+#define LOG_IT_AFTER 5          /* Number of iteration to log after
+                                   suspicious iteration. */
+
+bool log_on = 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)
@@ -133,6 +150,8 @@  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_begin_it = UINT64_MAX;
+    s->log_end_it = UINT64_MAX;
 }
 
 void
@@ -365,7 +384,129 @@  pmd_perf_stats_clear(struct pmd_perf_stats *s)
     histogram_clear(&s->max_vhost_qfill);
     history_init(&s->iterations);
     history_init(&s->milliseconds);
+    s->log_begin_it = UINT64_MAX;
+    s->log_end_it = UINT64_MAX;
     s->start_ms = time_msec(); /* Clearing finished. */
     s->milliseconds.sample[0].timestamp = s->start_ms;
 }
 
+void
+pmd_perf_log_suspicious_iteration(struct pmd_perf_stats *s,
+                                     uint64_t cycles,
+                                     char *reason)
+{
+    VLOG_WARN_RL(&latency_rl,
+                 "Suspicious iteration (%s): tsc=%"PRIu64
+                 " duration=%"PRIu64" us\n",
+                 reason, s->current.timestamp,
+                 (1000000L * cycles) / get_tsc_hz());
+    if (log_it_before + log_it_after > 0) {
+        if (s->log_begin_it == UINT64_MAX) {
+            s->log_begin_it =
+                    (s->iterations.idx + HISTORY_LEN - log_it_before)
+                        % HISTORY_LEN;
+        }
+        s->log_end_it =
+                (s->iterations.idx + log_it_after) % HISTORY_LEN;
+    }
+}
+
+void
+pmd_perf_log_iteration_neighborhood(struct pmd_perf_stats *s)
+{
+    struct ds log = DS_EMPTY_INITIALIZER;
+    pmd_perf_format_iteration_history(&log, s,
+            (s->log_end_it + HISTORY_LEN - s->log_begin_it) % HISTORY_LEN);
+    VLOG_WARN_RL(&latency_rl,
+                 "Neighborhood of suspicious iteration:\n"
+                 "%s", ds_cstr(&log));
+    ds_destroy(&log);
+    s->log_end_it = s->log_begin_it = UINT64_MAX;
+    if (log_it_before > 100 || log_it_after > 100) {
+        /* Reset to safe default values to avoid disturbance. */
+        log_it_before = LOG_IT_BEFORE;
+        log_it_after = LOG_IT_AFTER;
+    }
+}
+
+void
+pmd_perf_log_set_cmd(struct unixctl_conn *conn,
+                 int argc, const char *argv[],
+                 void *aux OVS_UNUSED)
+{
+    int it_before, it_after, us_thr, q_thr;
+    bool on;
+    bool usage = false;
+
+    on = log_on;
+    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], "-a")) {
+            it_after = strtol(argv[2], NULL, 10);
+            if (it_after < 0) {
+                it_after = 0;
+            } else if (it_before + it_after > HISTORY_LEN-1) {
+                it_after = HISTORY_LEN-1 - it_before;
+            }
+            argc -= 2;
+            argv += 2;
+        } else if (!strcmp(argv[1], "-b")) {
+            it_before = strtol(argv[2], NULL, 10);
+            if (it_before < 0) {
+                it_before = 0;
+            } else if (it_before > HISTORY_LEN-10) {
+                it_before = HISTORY_LEN-10;
+            }
+            argc -= 2;
+            argv += 2;
+        } else if (!strcmp(argv[1], "-q")) {
+            q_thr = strtol(argv[2], NULL, 10);
+            if (q_thr < 0) {
+                q_thr = 0;
+            }
+            argc -= 2;
+            argv += 2;
+        } else if (!strcmp(argv[1], "-us")) {
+            us_thr = strtol(argv[2], NULL, 10);
+            if (us_thr < 0) {
+                us_thr = 0;
+            }
+            argc -= 2;
+            argv += 2;
+        } else {
+            usage = true;
+            break;
+        }
+    }
+
+    if (usage) {
+        unixctl_command_reply_error(conn,
+                "Usage: ovs-appctl dpif-netdev/pmd-perf-log-set "
+                "[on|off] [-b before] [-a after] [-us usec] [-q qlen]");
+        return;
+    }
+
+    VLOG_INFO("pmd-perf-log-set: %s, before=%d, after=%d, us_thr=%d,"
+              " q_thr=%d\n",
+              on ? "on" : "off", it_before, it_after, us_thr, q_thr);
+    log_on = on;
+    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 01fde8d..442c94b 100644
--- a/lib/dpif-netdev-perf.h
+++ b/lib/dpif-netdev-perf.h
@@ -107,6 +107,8 @@  struct pmd_perf_stats {
     struct histogram max_vhost_qfill;
     struct history iterations;
     struct history milliseconds;
+    uint64_t log_begin_it;
+    uint64_t log_end_it;
 };
 
 enum pmd_info_type;
@@ -119,6 +121,10 @@  struct pmd_perf_params {
     size_t ms_hist_len;
 };
 
+extern bool log_on;
+extern uint32_t log_q_thr;
+extern uint64_t iter_cycle_threshold;
+
 void pmd_perf_stats_init(struct pmd_perf_stats *s);
 void pmd_perf_stats_clear(struct pmd_perf_stats *s);
 void pmd_perf_read_counters(struct pmd_perf_stats *s,
@@ -143,9 +149,17 @@  void pmd_perf_format_iteration_history(struct ds *str,
 void pmd_perf_format_ms_history(struct ds *str, struct pmd_perf_stats *s,
                                 int n_ms);
 
+void pmd_perf_log_suspicious_iteration(struct pmd_perf_stats *s,
+                                       uint64_t cycles,
+                                       char *reason);
+void pmd_perf_log_iteration_neighborhood(struct pmd_perf_stats *s);
 void pmd_perf_show(struct unixctl_conn *conn, int argc,
                    const char *argv[],
                    void *aux OVS_UNUSED);
+void pmd_perf_log_set_cmd(struct unixctl_conn *conn,
+                      int argc, const char *argv[],
+                      void *aux OVS_UNUSED);
+
 static inline void
 histogram_add_sample(struct histogram *hist, uint32_t val)
 {
@@ -208,6 +222,7 @@  pmd_perf_end_iteration(struct pmd_perf_stats *s, uint64_t now_tsc,
 {
     struct iter_stats *cum_ms;
     uint64_t cycles, cycles_per_pkt = 0;
+    char *reason = NULL;
 
     if (OVS_UNLIKELY(s->current.timestamp == 0)) {
         /* Stats were cleared during the ongoing iteration. */
@@ -256,6 +271,23 @@  pmd_perf_end_iteration(struct pmd_perf_stats *s, uint64_t now_tsc,
     cum_ms->batches += s->current.batches;
     cum_ms->max_vhost_qfill += s->current.max_vhost_qfill;
 
+    if (log_on) {
+        /* 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_log_suspicious_iteration(s, cycles, reason);
+        }
+
+        /* Log iteration stats interval when required. */
+        if (OVS_UNLIKELY(s->log_end_it == s->iterations.idx)) {
+            pmd_perf_log_iteration_neighborhood(s);
+        }
+    }
+
     /* Store in iteration history. */
     history_store(&s->iterations, &s->current);
     if (now_tsc - s->last_tsc > 10000) {
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 63a4139..e40a39e 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -1164,6 +1164,11 @@  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] "
+                             "[-us usec] [-q qlen]",
+                             0, 10, pmd_perf_log_set_cmd,
+                             NULL);
     return 0;
 }