[SR-Users] Dialog Module Hash Size vs Number of Dialogs

[Mark Blackford]

Thank you for your response!

I am currently replacing the call_control module used with CDRTool Prepaid
with the dialog module using hash tables. The speed and stability are
tremendously better!

My concern is two-fold:
1) I do not want calls to be blocked because I set the hash table size too
small.
2) I do not want any memory usage problems that could cause kamailio
stability issues.

My understanding, or at least how I want to use the "hash_size" modparam,
is that hash_size gives dialog a set memory space (aka slots and buckets)
to store the dialogs being tracked.  This is great since I "think" I will
have constant memory consumption that will be a fixed amount and never
"grow".  However, I wanted to get a rough idea of how many dialogs
(customer calls) I could track per kamailio instance to properly choose the
hash size.

I thought it would be easy to set the value to something very small in the
lab and just run up the number of calls until kamailio hits an upper limit
and fails to create any more dialogs.
modparam("dialog", "hash_size", 32)

However, I am able to create almost 2000 dialogs no matter what size I
choose.  After, reading the information in the link about hash tables and
your response, I see how a larger table with more "hashing" increases
lookup performance, but I still do not see how the total number of dialogs
that the module tracks can be set so that the kamailio memory usage is
protected.  I still look at the hash_size as the key here and that there
should be a relationship, perhaps rough at best, to the maximum number of
dialogs supported in the table.

Thanks so much for your time,
Mark Blackord
Digium Cloud Services

On Sat, Dec 2, 2017 at 2:50 AM, Daniel-Constantin Mierla <miconda at gmail.com>
wrote:

> Hello,
>
> hash size does not set any limitation to the number of dialogs (active
> calls), it has impact on searching the dialogs, so if you have a lot of
> active calls, increasing the hash size might improve performances.
> Effectively the hash size is used to compute the number of slots (aka
> buckets) the hash table is going to have, see more technical details about
> hash tables at:
>
>   - https://en.wikipedia.org/wiki/Hash_table
>
> Can you elaborate on your statement:
>
> > but even setting the hash size to a very tiny number does stop me from
> creating hundreds of dialogs
>
> Do you mean you are not able to create as many dialogs as you want?
>
> Cheers,
> Daniel
>
> On 01.12.17 19:54, Mark Blackford wrote:
>
> Hello,
>
> I am trying to properly size the use of the Dialog Module hash for our
> implementation using:
>
> modparam("dialog", "hash_size", <number that is power of two>)
>
> However, in my testing, I have been unable to figure out the relationship
> between the hash size and a number of dialogs I need to support.  I think
> the hash size is specifying a memory block in kB, but even setting the hash
> size to a very tiny number does stop me from creating hundreds of dialogs.
>
> Is there a way to determine a relationship between the hash size and a
> rough number of dialogs that would be expected?
>
> An example of a a dialog looks like this from kamctl:
>
> [root at kamailio01 ~]# kamctl dialog show
> dialog memory records
> dialog::  hash=22:70
> state:: 4
> ref_count:: 2
> timestart:: 1512151205
> timeout:: 36083666
> callid:: 0gQAAC8WAAACBAAALxYAAClws2wyL8GE+CSgRY7HIhmg9ZUIISZad46ntOPng3i
> PIcLaxzLFaytRTI7M0Bzz0g-- at 10.155.8.40
> from_uri:: sip:b53667d44239457fbc94fc2f4c4e25a6 at sip.dcs-staging.net
> from_tag:: 10.155.8.40+1+689d7e5e+8fcf481a
> caller_contact:: sip:43f0ae1480846185e8803f21e9f2b7
> 21 at 10.155.8.40:5060;transport=udp
> caller_cseq:: 24115
> caller_route_set::
> caller_bind_addr:: udp:10.155.8.11:5060
> callee_bind_addr:: udp:10.155.8.11:5060
> to_uri:: sip:2052773090 at sip.dcs-staging.net
> to_tag:: sip+1+bdcd0004+2038f37c
> callee_contact:: sip:ca2013e84f10348a1cc825c12562bd
> e7 at 10.155.8.40:5060;transport=udp
> callee_cseq:: 0
> callee_route_set::
>
>
>
> Thanks!
> --
> Mark Blackford
> Digium Cloud Services
> 678.230.8769
>
>
>
> _______________________________________________
> Kamailio (SER) - Users Mailing Listsr-users at lists.kamailio.orghttps://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>
>
> --
> Daniel-Constantin Mierlawww.twitter.com/miconda -- www.linkedin.com/in/miconda
> Kamailio Advanced Training - www.asipto.com
> Kamailio World Conference - May 14-16, 2018 - www.kamailioworld.com
>
>


-- 
Mark Blackford
Digium Cloud Services
678.230.8769
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