[RTEMS Project] #3582: Remove dedicated support for boundary constraint in heap allocator

RTEMS trac trac at rtems.org
Wed Nov 7 11:02:37 UTC 2018


#3582: Remove dedicated support for boundary constraint in heap allocator
------------------------------+-----------------------------
  Reporter:  Sebastian Huber  |      Owner:  Sebastian Huber
      Type:  task             |     Status:  assigned
  Priority:  normal           |  Milestone:  5.1
 Component:  score            |    Version:  5
  Severity:  normal           |   Keywords:
Blocked By:                   |   Blocking:
------------------------------+-----------------------------
 Some time ago a dedicated support for a boundary constraint was added to
 the first fit heap allocator. The use case for this is the libbsd (new
 network stack) which needs this for the bus space allocator:

 https://www.freebsd.org/cgi/man.cgi?query=bus_dma

 It turned out that this feature is rarely used. It makes the first fit
 heap allocator implementation considerably more complex. It is also not a
 standard allocator feature which makes it more difficult to replace the
 first fit heap allocator with something else, e.g. TLSF.

 The boundary constraint can be also satisfied by an allocator which
 supports only the alignment constraint via:
 {{{
 if (boundary > alignment) {
         assert(alignment == 0 || boundary % alignment == 0);
         alignment = boundary;
 }
 }}}

--
Ticket URL: <http://devel.rtems.org/ticket/3582>
RTEMS Project <http://www.rtems.org/>
RTEMS Project


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