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Bug #5552

closed

no overall limit of paging requests at BSC level

Added by laforge almost 2 years ago. Updated over 1 year ago.

Status:
Resolved
Priority:
Normal
Assignee:
Category:
A interface
Target version:
-
Start date:
05/06/2022
Due date:
% Done:

100%

Spec Reference:

Description

It seems we don't have any maximum queue depth for paging requests from the MSC. I've created a TTCN3 test that sends 100 new paging requests per second, and I can see the per-BTS paging queue grow to > 4000 entries, associated with the BSC spending all the CPU cycles it can get in _paging_request

 Paging: 4004 pending requests, 16 free slots 

I think there shold be some upper limit for the per-BTS paging queue at the BSC.


Related issues

Related to OsmoBSC - Bug #5553: dynamic T3113 has no reasonable upper boundResolvedpespin05/06/2022

Actions
Actions #1

Updated by pespin almost 2 years ago

It may make sense, once reached the threshold of the maximum amount of allowed requests, to try to drop one of the in-retransmission-state requests in the queue, and accept the new one.

Actions #2

Updated by laforge almost 2 years ago

  • Related to Bug #5553: dynamic T3113 has no reasonable upper bound added
Actions #3

Updated by pespin almost 2 years ago

Maximum paging length is already implemented since the last bunch of osmo-bsc paging improvements. See paging.c _paging_request():

#define MAX_TX_DELAY_TIME_SEC 60
[...]
    /* don't try to queue more requests than we can realistically handle within MAX_TX_DELAY_TIME_SEC seconds */
    if (paging_pending_requests_nr(bts) > paging_estimate_available_slots(bts, MAX_TX_DELAY_TIME_SEC)) {
        rate_ctr_inc(rate_ctr_group_get_ctr(bts->bts_ctrs, BTS_CTR_PAGING_OVERLOAD));
        return -ENOSPC;
    }

Some stuff we may want to improve here:
  • Make "MAX_TX_DELAY_TIME_SEC 60" configurable through VTY. This may be useful to configure it so that it matches some paging timeout config at the MSC?
  • When the queue is full, instead of dropping it, remove the first non-initial (retrans) entry from the list, then add this new paging req.
Actions #4

Updated by pespin over 1 year ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 50

pespin wrote in #note-3:

  • Make "MAX_TX_DELAY_TIME_SEC 60" configurable through VTY. This may be useful to configure it so that it matches some paging timeout config at the MSC?

https://gerrit.osmocom.org/c/osmo-bsc/+/30345

Actions #5

Updated by pespin over 1 year ago

  • Status changed from In Progress to Feedback
  • % Done changed from 50 to 90

pespin wrote in #note-3:

  • When the queue is full, instead of dropping it, remove the first non-initial (retrans) entry from the list, then add this new paging req.

Done here: https://gerrit.osmocom.org/c/osmo-bsc/+/30347

Ticket can be closed once merged.

Actions #6

Updated by pespin over 1 year ago

  • Status changed from Feedback to Resolved
  • % Done changed from 90 to 100

Merged, closing.

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