memory overhead of rtems regions

[Gedare Bloom]

Looking closer, your allocations are multiples of 40. You should set
the page_size to 40 in your region create.

On Thu, Mar 7, 2013 at 9:37 AM, Gedare Bloom <gedare at rtems.org> wrote:
> You're right. The error return does indicate that memory ran out. It's
> not clear if the memory that ran out is heap or workspace.
>
> You set a page_size of 128, and then make allocations in multiples of
> 10. I think the segments that get returned are allocated as multiples
> of the page_size. So there will be some fragmentation issues. E.g. a
> request for a segment of size 400 will return a 512 size segment,
> wasting 112 bytes. This is stated in the C User Manual section about
> Regions [1]. This fragmentation is probably causing the problem.
>
> -Gedare
>
> [1] http://rtems.org/onlinedocs/doc-current/share/rtems/html/c_user/Region-Manager-Region-Manager-Definitions.html#Region-Manager-Region-Manager-Definitions
>
> On Thu, Mar 7, 2013 at 9:21 AM, Matthew J Fletcher <amimjf at gmail.com> wrote:
>> Hi,
>>
>> Its 20, but I believe that would return RTEMS_TO_MANY, if that was not
>> enough.
>>
>> On 7 Mar 2013 14:09, "Gedare Bloom" <gedare at rtems.org> wrote:
>>>
>>> Check how many message queues your application has configured.
>>>
>>> #define CONFIGURE_MAXIMUM_MESSAGE_QUEUES    ?
>>>
>>> On Thu, Mar 7, 2013 at 7:05 AM, Matthew J Fletcher <amimjf at gmail.com>
>>> wrote:
>>> > Hi,
>>> >
>>> > Reading the documentation for rtems regions is a bit vague about the
>>> > overhead of the lists that behind the scenes manage the blocks. Its
>>> > quite
>>> > possible i am not fully understanding the operation. I have a call
>>> > sequence
>>> > as follows.
>>> >
>>> > rtems_region_create( length = 19800, page_size = 128 )
>>> >   rtems_region_get_segment( size = 160 )
>>> >     rtems_message_queue_create ( count = 160, max_size =2 )
>>> >   rtems_region_get_segment( size = 400 )
>>> >     rtems_message_queue_create ( count = 400, max_size =2 )
>>> >   rtems_region_get_segment( size = 1600 )
>>> >     rtems_message_queue_create ( count = 1600, max_size =2 )
>>> >   rtems_region_get_segment( size = 40 )
>>> >     rtems_message_queue_create ( count = 40, max_size =2 )
>>> >   rtems_region_get_segment( size = 4000 )
>>> >     rtems_message_queue_create ( count = 4000, max_size =2 )
>>> >   rtems_region_get_segment( size = 40 )
>>> >     rtems_message_queue_create ( count = 40, max_size =2 )
>>> >   rtems_region_get_segment( size = 40 )
>>> >     rtems_message_queue_create ( count = 40, max_size =2 )
>>> >   rtems_region_get_segment( size = 40 )
>>> >     rtems_message_queue_create ( count = 40, max_size =2 )
>>> >   rtems_region_get_segment( size = 40 )
>>> >     rtems_message_queue_create ( count = 40, max_size =2 )
>>> >   rtems_region_get_segment( size = 120 )
>>> >     rtems_message_queue_create ( count = 120, max_size =2 )
>>> >   rtems_region_get_segment( size = 400 )
>>> >     rtems_message_queue_create ( count = 400, max_size =2 )
>>> >   rtems_region_get_segment( size = 400 )
>>> >     rtems_message_queue_create ( count = 400, max_size =2 )
>>> >   rtems_region_get_segment( size = 2000 ) // total size upto here 7320
>>> >     rtems_message_queue_create ( count = 2000, max_size =2 )
>>> >     // returns RTEMS_UNSATISFIED - unable to allocate message buffers
>>> > here
>>> >
>>> > I dont fully understand why RTEMS_UNSATISFIED is being returned from the
>>> > queue_create(), is there really a 50%+ overhead in managing 128 byte
>>> > pages ?
>>> > out of a 19800 length.
>>> >
>>> > I am presuming that the RTEMS_UNSATISFIED is because of the region size,
>>> > but
>>> > i could be wrong about that.
>>> >
>>> >
>>> > regards
>>> > ---
>>> > Matthew J Fletcher
>>> >
>>> >
>>> > _______________________________________________
>>> > rtems-users mailing list
>>> > rtems-users at rtems.org
>>> > http://www.rtems.org/mailman/listinfo/rtems-users
>>> >