RE: Memory Problem related to CA?

["Jeff Hill" <johill@lanl.gov>]

Hello Bernd,

Yes, to avoid problems with fragmentation, the CA server does have several
free memory pools. As you suspect, the free lists that it uses are not
returned to the system pool, and so its memory usage high water mark will
persist even if the client load decreases. One can examine how much memory
it has in its pocket using the "casr" command specifying higher interest
levels.

With R3.13 there are more raw malloc/calloc requests in the ca server (that
don't use a free list) and so there is greater potential for fragmenting the
system memory pool. More recent versions of vxWorks use a best fit memory
allocation scheme so fragmentation of the system memory pool is less common,
but of course memory allocation overhead is also higher. You can examine
some statistics of the system memory pool with the "memShow" command.

> Can the channel access pool become fragmented? 

Probably not because it uses free lists - each of them dedicated to a
particular size of block that is needed.

Jeff

> -----Original Message-----
> From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov]
> On Behalf Of Schoeneburg, Bernd
> Sent: Friday, March 14, 2008 10:20 AM
> To: tech-talk@aps.anl.gov
> Subject: Memory Problem related to CA?
> 
> Hi all,
> on some IOCs we see that the free memory becomes less and less.
> Especially when we restart our channel archiver, the free memory in the
> IOCs becomes much less.
> My possible explanation for this is that channel access has not a free
> memory block of the desired (big) size in its private pool, so that
> additional memory from the system pool is allocated - and never free'd.
> Is this possible? Can the channel access pool become fragmented? If YES:
> Is there a solution for this in later versions? Or a patch?	
> 
> We are using Epics 3.13.10 with vxWorks 5.3.1 on mvme162-532A (16 MB)
> 
> Thank you
> 
> Bernd