[PATCH v1 1/2] PCI/AER: Use for_each_set_bit()

[David Howells]

Andy Shevchenko <andriy.shevchenko at linux.intel.com> wrote:

> > but I confess to being a little ambivalent.  It's
> > arguably a little easier to read,
> 
> I have another opinion here. Instead of parsing body of for-loop, the name of
> the function tells you exactly what it's done. Besides the fact that reading
> and parsing two lines, with zero conditionals, is faster.
> 
> > but it's not nearly as efficient
> > (not a great concern here)
> 
> David, do you know why for_each_set_bit() has no optimization for the cases
> when nbits <= BITS_PER_LONG? (Actually find_*bit() family of functions)

I've not had anything to do with for_each_set_bit() itself.

By 'nbits', I presume you mean the size parameter - max in the sample bit of
code.

It would need per-arch optimisation.  Some arches have an instruction to find
the next bit and some don't.

Using for_each_set_bit() like this is definitely suboptimal, since
find_first_bit() and find_next_bit() may well be out of line.

It should probably be using something like __ffs() if size <= BITS_PER_LONG.

David