[patch] bitmap.c: Speed up bitmap_find_bit.

[Jeffrey A Law]

On Thu, 2004-11-25 at 00:05 -0500, Kazu Hirata wrote:
> Hi,
> 
> Attached is a patch to speed up bitmap_find_bit.
> 
> Currently, bitmap_find_bit always traverses from head->current.  This
> approach tends to be slow if the we are looking for a bit that's
> closer to the beginning of the bitmap than to the "current element" of
> the bitmap.
> 
> The patch adds another way of traversal, namely from head->first.  We
> choose to traverse from head->first when the index of the element that
> contains the bit we are after is less than half of head->indx.
Before you install that patch you might do well to look at places
where we are doing random or semi-random queries into the bitmaps.
You'll likely get bigger improvements by avoiding the random
bitmap queries rather than by twidding the bitmap code itself.

Jeff