memory overhead of rtems regions

[Matthew J Fletcher]

Well easy for me as I know my allocation sizes ;-)
 On 7 Mar 2013 16:55, "Gedare Bloom" <gedare at rtems.org> wrote:

> Matthew,
>
> Is there an easy way to find this optimal size? If so maybe you could
> post it or better yet document it in the region documentation :)
>
> On Thu, Mar 7, 2013 at 11:44 AM, Matthew J Fletcher <amimjf at gmail.com>
> wrote:
> > Gedare,
> >
> > Thanks for the advice, for this particular region that's the optimal
> size,
> > I've done a bit of experimentation and you can find an optimal size for
> most
> > allocations.
> >
> > On 7 Mar 2013 14:38, "Gedare Bloom" <gedare at rtems.org> wrote:
> >>
> >> 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
> >> >>> >
>
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