On 12/1/06, Paul Jackson <[email protected]> wrote:
M. R. Brown and Paul Mundt -- take a look at the question at end of this post.
Komal wrote:
>
> I have attached the test module code. I have confusion about the what
> to pass as second argument of bitmap_find_free_region for 2nd layer
> bitmap.
>
> Do we have to pass "total size of the block...here 128MB" as the
> second argument or no. of bits in that block, which 32768 (128 >>
> PAGE_SHIFT) ?
>
> This confusion arised as store queue implementation (sq.c) of sh arch,
> passes total size of the bitmap (64M) as the second argument instead
> of bits.
>
> Same is the case with bitmap_full, where I have to pass total size of
> the block (here 128MB) instead of no. of bits, in-order it to make my
> test module work correctly.
A bitmap is essentially an array of bits. The bitmap_* routines should
take a count of how many bits are in the bitmap array (or in your case,
how many bits are in the segment that you expect to be used in that call.)
So I'm guessing you will be passing L2_BM_BITS for that second argument.
The call to bitmap_find_free_region(), in arch/sh/kernel/cpu/sh4/sq.c
looks bogus:
page = bitmap_find_free_region(sq_bitmap, 0x04000000,
get_order(map->size));
It says the bitmap has 0x04000000 bits. This would take 0x04000000 / 8
which is 8388608 (decimal) bytes to hold. That's an insanely
huge bitmap - 8 million bytes worth of bits.
I can't make entire sense of the the code you attached. I get confused
over the various sizes of maps and what the maps represent, and of bits
and bytes, and of the two levels.
Thanx for clarifying. I am now able to understand it properly, and I
will modify my code, so that it will be easy to understand/read :)
--
---Komal Shah
http://komalshah.blogspot.com
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