Re: [Xenomai-help] rt_queue_write error: "Cannot allocate memory "; bug or feature ?

[Philippe Gerum <rpm@xenomai.org>]

Roderik.Wildenburg@domain.hid wrote:
> When running the attached programm for a while I get an "Cannot allocate memory" error with the function rt_queue_write.

What is the exact size of the message rt_queue_write() fails to send, as
displayed by your trace?

> I can´t see any obvious mistake in my code, so I don´t have an simple explanation for this behavior but just a suspicion (see below). Could somebody be so kind to try to reproduce this problem, so I can determine whether this is a problem of my context or of xenomai. 
> I use Xenomai 2.3.2 with an 2.4.25 kernel on PPC.
> 
> Or, even better, could somebody explain to me the functionality of heap allocation of native queues.

Message buffers are simply obtained from a memory pool managed as a
nucleus heap. rt_queue_write() allocates a message block from the pool
to hold the emitted data, and pushes it to the pending message queue,
rt_queue_read() then pops the next available message from this queue,
copies the payload data to the user-space buffer, and frees the message
block.

I have the impression the problem of my program results from some kind
of heap fragmentation,
as I write very differnt buffersizes to a quite small queue (see code
line 59-62).
> 

It's unlikely, since the consumer thread has absolute priority (50) over
the producer in your code (30); in such a case, the buffer pool should
only have a single busy message block at any given time.

You may want to display /proc/xenomai/registry/native/queues/qtest1q
periodically, while your test program is running, and check the usedmem
field. If it indeed decreases over time, then there is a memory leak
somewhere.

-- 
Philippe.