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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 it is more important to transmit
intial requests than to retransmit already transmitted ones. The
rationale is that there's lower chances that 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.

Change-Id: Idfd93254ae456b1ee08416e05479488299dd063d
Related: OS#5552
This commit is contained in:
Pau Espin 2022-11-29 11:51:41 +01:00
parent e2438ade54
commit 1e7dd5c0bb
1 changed files with 14 additions and 7 deletions
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21
src/osmo-bsc/paging.c
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@ -504,13 +504,6 @@ static int _paging_request(const struct bsc_paging_params *params, struct gsm_bt
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. */
if (paging_pending_requests_nr(bts) > paging_estimate_available_slots(bts, x3113_s)) {
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");
@ -518,6 +511,20 @@ static int _paging_request(const struct bsc_paging_params *params, struct gsm_bt
return -EEXIST;
}
/* Don't try to queue more requests than we can realistically handle within X3113 seconds,
* see PAGING_THRESHOLD_X3113_DEFAULT_SEC. */
if (paging_pending_requests_nr(bts) > paging_estimate_available_slots(bts, x3113_s)) {
struct gsm_paging_request *first_retrans_req;
rate_ctr_inc(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_PAGING_OVERLOAD));
/* Need to drop a retrans from the queue if possible, in order to make space for the new initial req. */
if (bts_entry->retrans_req_list_len == 0) {
/* There are no retrans to be replaced by this initial request, discard it. */
return -ENOSPC;
}
first_retrans_req = llist_first_entry(&bts_entry->retrans_req_list, struct gsm_paging_request, entry);
paging_remove_request(first_retrans_req);
}
/* The incoming new req will be stored in initial_req_list giving higher prio
* to it over retransmissions. This avoids new subscribers being paged to
* be delayed if the paging queue is full due to a lot of retranmissions.