Gilles Chanteperdrix wrote: > Jan Kiszka wrote: > > Hi, > > > > playing a stupid rt_heap user (actually I didn't just play this...), I > > stumbled over this undocumented oddity: > > > > rt_heap_create(&heap, name, 10000, H_PRIO|H_MAPPABLE); > > rt_heap_alloc(&heap, 10000, TM_NONBLOCK, &ptr); > > > > Creation is successful, allocation fails. The reason: while during > > creation the net heap size is rounded down to page boundaries, the > > allocation of memory > PAGE_SIZE is rounded up. One could add H_SINGLE > > to the flags, but this may even result in allocating less memory than > > the user expected, causing severe problems later. > > > > How to resolve this best? I thought about rounding twice in > > rt_head_create (one time the net size, the second time including the > > overhead), but this encodes characteristics of the underlying heap > > allocator into the skin (I have a generic heap allocator framework in > > mind for 2.3). So I decided to do this rounding in xnheap_overhead() > > instead, see attached patch. Hope I didn't skewed up any calculation. At > > least the scenario above now works fine. > > The problem I see with this patch is that you are counting > (rounded_hsize - hsize) as part of the overhead, whereas you would like to > count it as free space. Would not it make more sense to do the rounding > in xnheap_init_mapped ? >
I was thinking of the open-coded allocate(heap_size + xnheap_overhead) xnheap_init() in many skins as well. Jan
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