stats: new trackers for lchan life duration (v2)

This patch adds two stats which track cummulative lchan lifetime by
type TCH and SDCCH. These new counters will accomplish two things:

1) Provide a glanceable way to see if lchan durations look healthy. When
examining a site, short-lived (<5s) and long-lived (>30s) TCH lchans
are difficult to tell apart. If we only see short-lived TCH lchans,
there is most likely an RF or signaling problem to investigate. This
new counter will expose channel ages in the VTY output

2) Provide a more accurate count for Erlangs per site. Currently, we
are basing Erlangs on active TCH channel counts per stats period. This
method skews high very quickly. Each active TCH in that period
translates into the full 10s of activity. This counter should improve
accuracy by two orders of magnitude.

Change-Id: Ie3771233ecbd4bc24a24fb22c1064a18e7b8b2b0

1 files changed, 61 insertions, 0 deletions

diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c
index c04a59ec0..ad46f54f9 100644
--- a/src/osmo-bsc/bts.c
+++ b/src/osmo-bsc/bts.c
@@ -741,6 +741,61 @@ void bts_store_uptime(struct gsm_bts *bts)
 	osmo_stat_item_set(osmo_stat_item_group_get_item(bts->bts_statg, BTS_STAT_UPTIME_SECONDS), bts_uptime(bts));
 }
 
+void bts_store_lchan_durations(struct gsm_bts *bts)
+{
+	struct gsm_bts_trx *trx;
+	int i, j;
+	struct timespec now, elapsed;
+	uint64_t elapsed_ms;
+	uint64_t elapsed_tch_ms = 0;
+	uint64_t elapsed_sdcch_ms = 0;
+
+	/* Ignore BTS that are not in operation. */
+	if (!trx_is_usable(bts->c0))
+		return;
+
+	/* Grab storage time to be used for all lchans. */
+	osmo_clock_gettime(CLOCK_MONOTONIC, &now);
+
+	/* Iterate over all lchans. */
+	llist_for_each_entry(trx, &bts->trx_list, list) {
+		for (i = 0; i < ARRAY_SIZE(trx->ts); i++) {
+			struct gsm_bts_trx_ts *ts = &trx->ts[i];
+			for (j = 0; j < ARRAY_SIZE(ts->lchan); j++) {
+				struct gsm_lchan *lchan = &ts->lchan[j];
+
+				/* Ignore lchans whose activation timestamps are not yet set. */
+				if (lchan->active_stored.tv_sec == 0 && lchan->active_stored.tv_nsec == 0)
+					continue;
+
+				/* Calculate elapsed time since last storage. */
+				timespecsub(&now, &lchan->active_stored, &elapsed);
+				elapsed_ms = elapsed.tv_sec * 1000 + elapsed.tv_nsec / 1000000;
+
+				/* Assign elapsed time to appropriate bucket. */
+				switch (lchan->type) {
+				case GSM_LCHAN_TCH_H:
+				case GSM_LCHAN_TCH_F:
+					elapsed_tch_ms += elapsed_ms;
+					break;
+				case GSM_LCHAN_SDCCH:
+					elapsed_sdcch_ms += elapsed_ms;
+					break;
+				default:
+					continue;
+				}
+
+				/* Update storage time. */
+				lchan->active_stored = now;
+			}
+		}
+	}
+
+	/* Export to rate counters. */
+	rate_ctr_add(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_CHAN_TCH_ACTIVE_MILLISECONDS_TOTAL), elapsed_tch_ms);
+	rate_ctr_add(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_CHAN_SDCCH_ACTIVE_MILLISECONDS_TOTAL), elapsed_sdcch_ms);
+}
+
 unsigned long long bts_uptime(const struct gsm_bts *bts)
 {
 	struct timespec tp;
@@ -1099,6 +1154,12 @@ const struct rate_ctr_desc bts_ctr_description[] = {
 	[BTS_CTR_CHAN_ACT_NACK] = \
 		{ "chan_act:nack",
 		  "Number of Channel Activations that the BTS NACKed" },
+	[BTS_CTR_CHAN_TCH_ACTIVE_MILLISECONDS_TOTAL] = \
+		{ "chan_tch:active_milliseconds:total",
+		  "Cumulative number of milliseconds of TCH channel activity" },
+	[BTS_CTR_CHAN_SDCCH_ACTIVE_MILLISECONDS_TOTAL] = \
+		{ "chan_sdcch:active_milliseconds:total",
+		  "Cumulative number of milliseconds of SDCCH channel activity" },
 	[BTS_CTR_RSL_UNKNOWN] = \
 		{ "rsl:unknown",
 		  "Number of unknown/unsupported RSL messages received from BTS" },