[SR-Users] Shared memory fragmentation

[Morten Isaksen]

Hi Daniel and Marius,

Thanks for your feedback.

I hope I have solved the issue. Due to a bug in the perl script that
generated the route table some destinations got added instead of
updated to the table. The result of this bug was that about 50
destinations each was 1082 times in the route table.

/Morten

On Fri, Jun 8, 2012 at 4:51 PM, Marius Zbihlei <marius.zbihlei at 1and1.ro> wrote:
> On 06/08/2012 03:09 PM, Morten Isaksen wrote:
>>
>> Hi,
>
> Hello,
>
>
>> We have 2 Kamailio 3.0.3 servers that has been running with
>> carrierroute for about 2 years without any problems. They have 128 MB
>> shared memory and
>
> The shared memory is too little. Keep in mind that this is shared by all
> children, so it will not increase with the creating of more children. Also
> keep in mind that the Linux memory alocator (like for mmap) is lazy, so
> allocating 1 GB by the application will not use 1 GB of RAM, but instead
> pages will be delivered to the application as it needs it. To force
> allocation there is the shm_force_alloc core parameter to really force
> allocation of memory by the system bye writing 0's to the memory reagion.
> Also there is the mlock_pages parameter that will force the allocated memory
> pages to not be swappable.
>
>> modparam("carrierroute", "config_source", "db")
>> modparam("carrierroute", "db_url", "<DBURL>")
>> modparam("carrierroute", "fetch_rows", 500)
>
>
> Fetch_rows is affects the private memory used when loading data from a data
> source that has the fetch result capability. This decreases the private
> memory requirements for reloading the table.
>
>>
>> The carrierroute table is about 91K lines and have been growing slowly.
>
>
> From experience this takes around 60-70 MB of shared memory to hold it.
>  This depends a lot based on system (32 vs 64 for example), structure etc.
>
>
>>
>> Suddenly we get this ERROR: carrierroute [cr_data.c:585]: could not
>> allocate shared memory from available pool after a few "kamctl cr
>> reload".
>>
>> I increased the shared memory to 256 MB but with the same result. I
>> have now increased it to 512 MB and it seems to work better now.
>>
>> I have noticed this. After a restart the shmem counters is like this:
>>
>> shmem:total_size = 536870912
>> shmem:used_size = 28486752
>> shmem:real_used_size = 40147128
>> shmem:max_used_size = 41135424
>> shmem:free_size = 496723784
>> shmem:fragments = 555
>>
>> And after the first "kamctl cr reload" it is like this:
>>
>> shmem:total_size = 536870912
>> shmem:used_size = 28619016
>> shmem:real_used_size = 51842768
>> shmem:max_used_size = 76993616
>> shmem:free_size = 485028144
>> shmem:fragments = 722063
>>
> I would worry if the used_size or real_used_size would have changed a lot.
> The difference from used_size to real_used_size is due to fragmentation but
> this will be manageable if the number of fragments is kept constant. As
> Daniel suggested, for carrierroute reload we need double the amount of
> memory as it holds the old and the new tables until it swaps the pointers
> (so that the applications doesn't block when reloading the table).
>
>
>> Notice the increase in fragments. Sequentials "kamctl cr reload" does
>> not change the fragments allot.
>>
>> Any ideas?
>
>
> I would recommend using kamailio with at least 1 GB of shared memory. Also
> monitor the used_size and real_used_size  if they are increasing in a
> `weird` way. The real_used_size might increase because of fragmentation
> during cr_reload_route commands, but it should not fail, as chunks will be
> reallocated to other usages of the command.
>
>
>
> Cheers,
> Marius
>
> --
> Zbihlei Marius
>
> Head of
> Linux Development Services Romania
>
> 1&1 Internet Development srl    Tel KA: 754-9152
> Str Mircea Eliade 18            Tel RO: +40-31-223-9152
> Sect 1, Bucuresti               mailto: marius.zbihlei at 1and1.ro
> 71295, Romania
>
>
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-- 
Morten Isaksen