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We saw in a recent prod setup a BSC with saturated channels. Further
investigation lead to a AGCH queue of 1000 (previous hard_limit)
messages, most of them being regular IMM ASSIGN (non REJ). Hence, we
also want to get rid of other messages in the AGCH queue (like regular
IMM ASSIGN).
Furthermore, In this scenario, sending IMM ASS REJ is as important as other
messages given than nowadays we support dynamic wait indicatior
(calculated based on chan load), which means if we reach the MS, we can
tell it to wait for a long time to reach us again, which is desirable.
Change-Id: I022b8948da8be13fb8f4bc36e7c9dab11c35fddb
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In a prod setup, complete channel saturation at the bsc was detected,
and Immediate Assignments were not being answered by the MS once sent by
the BTS.
Further investigation showed that the BTS was all the time printing
messages like this:
"bts.c:540 AGCH: too many messages in queue, refusing message type 0x3f, length = 1001/10"
So it seems the AGCH queue was becoming incredibly full (1000, hard
limit triggered the log), while acgch_queue.max_length was set to 10.
As a result, most probably the Immediate Assignments being sent to the
MS are super old in time, and the MS doesn't known about them anymore
once they are receivied, so no answer is sent back.
Let's try to avoid that by decreasing the hard limit so we never reach
that big queue_len scenario.
The number 100 is selected from data gatherered in agch_test.c which
prints a table of max_length values based on different setups. Some
values can reach around 80 messages, so let's use a slightly bigger hard
limit.
Related: SYS#2695
Change-Id: I272798c959abec123776d2fa8dad5685ec512fbd
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This patch implements merging of IMMEDIATE ASSIGN REJECT messages as
suggested in GSM 08.58, 5.7. When a new IMM.ASS.REJ is to be appended
to the AGCH queue and the last message in that queue is of the same
type, the individual entries (up to 4 per message) of both messages
are extracted, combined and stored back. If there are less than 5
entries, all entries fit into the old message and the new one is
discarded. Otherwise, the old message will contain 4 entries and the
remaining ones are stored into the new one which is then appended to
the queue.
Ticket: SYS#224
Sponsored-by: On-Waves ehf
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Currently, the AGCH queue length is not limited. This can lead to
large delays and network malfunction if there are many IMM.ASS.REJ
messages.
This patch adds two features:
- Don't accept msgs from the RSL layer when the queue is way too
full (safety measure, mainly if bts_ccch_copy_msg() is not being
called by the L1 layer, currently hard coded to 1000 messages)
- Selectively drop IMM.ASS.REJ from the queue output depending on the
queue length
Ticket: SYS#224
Sponsored-by: On-Waves ehf
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This patch extends paging_gen_msg() by adding an output parameter
is_empty that is true, if only a paging message with dummy entries
has been placed into buffer. This feature is then used by
bts_ccch_copy_msg() to insert an AGCH message if is_empty is true.
Ticket: SYS#224
Sponsored-by: On-Waves ehf
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The first test checks the AGCH may queue length computation.
The second test fills the queue by calling bts_agch_enqueue() with a
mix of IMM.ASS and IMM.ASS.REJ. Then it drains the queue by calling
bts_ccch_copy_msg(). After each of both steps, statistics are printed
out.
Sponsored-by: On-Waves ehf
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