Comments inline.
On 04.01.2018 15:07, 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] [-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 <[email protected]>
> ---
> lib/dpif-netdev-perf.c | 142
> +++++++++++++++++++++++++++++++++++++++++++++++++
> lib/dpif-netdev-perf.h | 32 +++++++++++
> lib/dpif-netdev.c | 5 ++
> 3 files changed, 179 insertions(+)
>
> diff --git a/lib/dpif-netdev-perf.c b/lib/dpif-netdev-perf.c
> index a66a48c..3fd19b0 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
> @@ -368,6 +387,129 @@ 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 3611723..392ca80 100644
> --- a/lib/dpif-netdev-perf.h
> +++ b/lib/dpif-netdev-perf.h
> @@ -109,6 +109,8 @@ 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;
> @@ -121,6 +123,10 @@ 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,
> @@ -145,9 +151,17 @@ 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)
> {
> @@ -210,6 +224,7 @@ 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. */
> @@ -263,6 +278,23 @@ 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) {
Can this be handled by the 'VLOG' module? I could be nice to control using
vlog/set command.
Something like:
if (VLOG_IS_WARN_ENABLED())
Default log level could be set to critical to avoid overhead.
> + /* 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 8f64df3..96cc4d5 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -1201,6 +1201,11 @@ 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;
> }
>
>
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