sched: energy saving: Avoid Tx dummy blocks on empty PDCH TS
Related: SYS#4919
Related: OS#4772
Change-Id: I8d66dd5e838748611e7b77b504fc86295f02c019
diff --git a/src/gprs_rlcmac_sched.cpp b/src/gprs_rlcmac_sched.cpp
index 5427e52..00f740e 100644
--- a/src/gprs_rlcmac_sched.cpp
+++ b/src/gprs_rlcmac_sched.cpp
@@ -485,12 +485,28 @@
gsmtap_cat = tx_is_egprs ? PCU_GSMTAP_C_DL_DATA_EGPRS :
PCU_GSMTAP_C_DL_DATA_GPRS;
}
- /* Prio 3: send dummy contol message */
- else if ((msg = sched_dummy())) {
- /* increase counter */
- gsmtap_cat = PCU_GSMTAP_C_DL_DUMMY;
- } else {
- return -ENOMEM;
+ /* Prio 3: send dummy control message if need to poll or USF */
+ else {
+ /* If there's no TBF attached to this PDCH, we can early skip
+ * since there's nothing to transmit nor to poll/USF. This way
+ * we help BTS energy saving (on TRX!=C0) by sending nothing
+ * instead of a dummy block. The early return is done here and
+ * not at the start of the function because the condition below
+ * (num_tbfs==0) may not be enough, because temporary dummy TBFs
+ * created to send Imm Ass Rej (see handle_tbf_reject()) don't
+ * have a TFI assigned and hence are not attached to the PDCH
+ * TS, so they don't show up in the count below.
+ */
+ const unsigned num_tbfs = pdch->num_tbfs(GPRS_RLCMAC_DL_TBF)
+ + pdch->num_tbfs(GPRS_RLCMAC_UL_TBF);
+ if (trx != 0 && num_tbfs == 0)
+ return 0;
+ if ((msg = sched_dummy())) {
+ /* increase counter */
+ gsmtap_cat = PCU_GSMTAP_C_DL_DUMMY;
+ } else {
+ return -ENOMEM;
+ }
}
if (tx_is_egprs && pdch->has_gprs_only_tbf_attached()) {