wasteful might have been a poor choice of words, but what I mean is that since I'm not using complex pattern, i.e. just filling with zero using fill seems a bit overkill.
The Buffer sizes is in ranges between ~64KB and ~128MB. Using a small pattern a float seems to be rather inefficient because even if it zero:ed it still need to do size/4 memcopies. Thats why I thought maybe using unmap/map and memset might be faster, I guess my best option is to time it and compare. (or something similar to that)