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In a 2.4 kernel, mm/page_alloc.c:free_area_init_core(), in the following
assignement...

bitmap_size = size >> i;

...makes bitmap_size be the double of the needed size, this calculum
assumes that with a 512 byte map size the kernel is mapping 8*512= 4096 chunks
of memory, that is: one bit of the map is used for each chunk of memory,
and that's not true.

Really one bit of area->map is used to map two chunks of memory, so in the
example above an area->map of just 256 bytes is really needed, the other 256
bytes are _never accessed_.

So the righ thing would be to do is:

bitmap_size = size >> (i+1);


also I tested it and it works ok, so I believe I'm right...


Please CC: your replies to (I'm not subscribed to this list)

Ulisses Alonso Camaró <uaca@NOSPAM.alumni.uv.es>

PD: my nick on #kernelnewbies is despistao

Debian GNU/Linux: a dream come true
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