pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bsc/+/30347 ) Change subject: paging: Replace reqs waiting for retransmission with new incoming inital req if queue is full ...................................................................... paging: Replace reqs waiting for retransmission with new incoming inital req if queue is full If queue size (in transmit delay of requests) is too long (above threshold) when a new initial incoming request arrives, instead of directly discarding it, see if we can drop a pending retransmission and insert the new one instead, in order to avoid losing initial requests. This is done under the assumption that is it more important to transmit intial requests than to retransmit already transmitted ones. The rationale is that there's lower chances than an MS which didn't answer lately will answer now (aka being reachable at the cell), so it's better to allocate resources for new requests (new MS) which may be available in the cell. Related: OS#5552 Change-Id: Idfd93254ae456b1ee08416e05479488299dd063d --- M src/osmo-bsc/paging.c 1 file changed, 42 insertions(+), 8 deletions(-) git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/47/30347/1 diff --git a/src/osmo-bsc/paging.c b/src/osmo-bsc/paging.c index 32ae627..50cc1ed 100644 --- a/src/osmo-bsc/paging.c +++ b/src/osmo-bsc/paging.c @@ -416,17 +416,10 @@ unsigned int reqs_before = 0, reqs_before_same_pgroup = 0; uint8_t pgroup = gsm0502_calc_paging_group(&bts->si_common.chan_desc, str_to_imsi(params->bsub->imsi)); + bool queue_full = false; rate_ctr_inc(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_PAGING_ATTEMPTED)); - /* Don't try to queue more requests than we can realistically handle within X3113 seconds, - * see PAGING_THRESHOLD_X3113_DEFAULT_SEC. */ - OSMO_ASSERT(td_x3113); - if (paging_pending_requests_nr(bts) > paging_estimate_available_slots(bts, td_x3113->val)) { - rate_ctr_inc(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_PAGING_OVERLOAD)); - return -ENOSPC; - } - /* Find if we already have one for the given subscriber on this BTS: */ if (bsc_subscr_find_req_by_bts(params->bsub, bts)) { LOG_PAGING_BTS(params, bts, DPAG, LOGL_INFO, "Paging request already pending for this subscriber\n"); @@ -434,6 +427,22 @@ return -EEXIST; } + /* Don't try to queue more requests than we can realistically handle within X3113 seconds, + * see PAGING_THRESHOLD_X3113_DEFAULT_SEC. */ + OSMO_ASSERT(td_x3113); + if (paging_pending_requests_nr(bts) > paging_estimate_available_slots(bts, td_x3113->val)) { + struct gsm_paging_request *last_req; + rate_ctr_inc(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_PAGING_OVERLOAD)); + OSMO_ASSERT(!llist_empty(&bts_entry->pending_requests)); + last_req = llist_last_entry(&bts_entry->pending_requests, struct gsm_paging_request, entry); + if (last_req->attempts == 0) { + /* Queue is full of initial requests, discard new one */ + return -ENOSPC; + } + /* There's at least 1 retrans. Flag to remove first retrans in queue once found below. */ + queue_full = true; + } + /* Find the last not-yet-ever-once-transmitted request; the new request * will be added immediately after it, giving higher prio to initial * transmissions (no retrans). This avoids new subscribers being paged to @@ -465,6 +474,31 @@ reqs_before_same_pgroup++; } + /* Need to drop a retrans from the queue if possible, in order to make space for the new initial req. */ + if (queue_full) { + if (!last_initial_req) { + /* Queue is full of retransmissions only, drop first one to free some space: */ + struct gsm_paging_request *first_retrans_req; + first_retrans_req = llist_first_entry_or_null(&bts_entry->pending_requests, struct gsm_paging_request, entry); + OSMO_ASSERT(first_retrans_req); + reqs_before--; + if (first_retrans_req->pgroup == pgroup) + reqs_before_same_pgroup--; + paging_remove_request(first_retrans_req); + } else { + struct gsm_paging_request *last_req; + last_req = llist_last_entry(&bts_entry->pending_requests, struct gsm_paging_request, entry); + OSMO_ASSERT(last_req); + if (&last_initial_req->entry == llist_last(&bts_entry->pending_requests)) { + /* Queue is full of initial requests only, discard the current new req: */ + return -ENOSPC; + } + /* We checked beforehand (set queue_full = true) that queue contains a retrans. + * Hence queue contains [1..N intials, 1..N retrans]: Drop first retransmission to free some space: */ + paging_remove_request(llist_entry(last_initial_req->entry.next, struct gsm_paging_request, entry)); + } + } + LOG_PAGING_BTS(params, bts, DPAG, LOGL_DEBUG, "Start paging\n"); req = talloc_zero(tall_paging_ctx, struct gsm_paging_request); OSMO_ASSERT(req); -- To view, visit https://gerrit.osmocom.org/c/osmo-bsc/+/30347 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-bsc Gerrit-Branch: master Gerrit-Change-Id: Idfd93254ae456b1ee08416e05479488299dd063d Gerrit-Change-Number: 30347 Gerrit-PatchSet: 1 Gerrit-Owner: pespin <pespin(a)sysmocom.de> Gerrit-MessageType: newchange