fix performance for chan_counts and all_allocated stats

The all_allocated_update_bsc() does inefficient iterating to count
active/inactive lchans, which scales badly for high numbers of TRX
managed by osmo-bsc.

We need to update the all_allocated flags immediately (periodic counting
alone would suffer from undersampling), so, until now, we are calling
this inefficient function every time a channel state changes.

Instead of iterating all channels for any chan state changes anywhere,
keep global state of the current channel counts, and on channel state
change only update those ts, trx, bts counts that actually change.

A desirable side effect: for connection stats and handover decision 2,
we can now also use the globally updated channel counts and save a bunch
of inefficient iterations.

To get accurate channel counts at all times, spread around some
chan_counts_ts_update() calls in pivotal places. It re-counts the given
timeslot and cascades counter changes, iff required.

Just in case I missed some channel accounting, still run an inefficient
iterating count regularly that detects errors, logs them and fixes them.
No real harm done if such error appears. None show in ttcn3 BSC_Tests.
It is fine to do the inefficient iteration once per second; channel
state changes can realistically happen hundreds of times per second.

Related: SYS#5976
Change-Id: I580bfae329aac8d4552723164741536af6512011

1 files changed, 39 insertions, 4 deletions

diff --git a/include/osmocom/bsc/chan_counts.h b/include/osmocom/bsc/chan_counts.h
index 31a1adc92..c11473e71 100644
--- a/include/osmocom/bsc/chan_counts.h
+++ b/include/osmocom/bsc/chan_counts.h
@@ -3,6 +3,14 @@
 
 struct gsm_bts;
 struct gsm_bts_trx;
+struct gsm_bts_trx_ts;
+struct gsm_lchan;
+
+void chan_counts_sig_init();
+void chan_counts_ts_update(struct gsm_bts_trx_ts *ts);
+void chan_counts_ts_clear(struct gsm_bts_trx_ts *ts);
+void chan_counts_trx_update(struct gsm_bts_trx *trx);
+void chan_counts_bsc_verify();
 
 /* First array index to chan_counts.val. */
 enum chan_counts_dim1 {
@@ -29,17 +37,29 @@ enum chan_counts_dim2 {
 };
 
 struct chan_counts {
-	unsigned int val[_CHAN_COUNTS1_NUM][_CHAN_COUNTS2_NUM][_GSM_LCHAN_MAX];
+	/* Signed type, so that chan_counts_diff() can return negative values. */
+	int val[_CHAN_COUNTS1_NUM][_CHAN_COUNTS2_NUM][_GSM_LCHAN_MAX];
 };
 
-void chan_counts_for_bts(struct chan_counts *bts_counts, const struct gsm_bts *bts);
-void chan_counts_for_trx(struct chan_counts *trx_counts, const struct gsm_bts_trx *trx);
-
 static inline void chan_counts_zero(struct chan_counts *counts)
 {
 	*counts = (struct chan_counts){0};
 }
 
+static inline bool chan_counts_is_zero(const struct chan_counts *counts)
+{
+	int i1, i2, i3;
+	for (i1 = 0; i1 < _CHAN_COUNTS1_NUM; i1++) {
+		for (i2 = 0; i2 < _CHAN_COUNTS2_NUM; i2++) {
+			for (i3 = 0; i3 < _GSM_LCHAN_MAX; i3++) {
+				if (counts->val[i1][i2][i3])
+					return false;
+			}
+		}
+	}
+	return true;
+}
+
 static inline void chan_counts_dim3_add(struct chan_counts *dst,
 					enum chan_counts_dim1 dst_dim1, enum chan_counts_dim2 dst_dim2,
 					const struct chan_counts *add,
@@ -68,9 +88,24 @@ static inline void chan_counts_dim2_add(struct chan_counts *dst, enum chan_count
 		chan_counts_dim3_add(dst, dst_dim1, i, add, add_dim1, i);
 }
 
+static inline void chan_counts_dim2_sub(struct chan_counts *dst, enum chan_counts_dim1 dst_dim1,
+					const struct chan_counts *sub, enum chan_counts_dim1 sub_dim1)
+{
+	int i;
+	for (i = 0; i < _CHAN_COUNTS2_NUM; i++)
+		chan_counts_dim3_sub(dst, dst_dim1, i, sub, sub_dim1, i);
+}
+
 static inline void chan_counts_add(struct chan_counts *dst, const struct chan_counts *add)
 {
 	int i;
 	for (i = 0; i < _CHAN_COUNTS1_NUM; i++)
 		chan_counts_dim2_add(dst, i, add, i);
 }
+
+static inline void chan_counts_sub(struct chan_counts *dst, const struct chan_counts *sub)
+{
+	int i;
+	for (i = 0; i < _CHAN_COUNTS1_NUM; i++)
+		chan_counts_dim2_sub(dst, i, sub, i);
+}