On Tue, 2013-01-08 at 18:38 -0800, Michel Lespinasse wrote:
>
> Well no fair, the previous patch (for powerpc as well) has 22
> insertions and 93 deletions :)
>
> The benefit is that the new code has lower algorithmic complexity, it
> replaces a per-vma loop with O(N) complexity with an outer loop that
> finds contiguous slice blocks and passes them to vm_unmapped_area()
> which is only O(log N) complexity. So the new code will be faster for
> workloads which use lots of vmas.
>
> That said, I do agree that the code that looks for contiguous
> available slices looks kinda ugly - just not sure how to make it look
> nicer though.
Ok. I think at least you can move that construct:
+ if (addr < SLICE_LOW_TOP) {
+ slice = GET_LOW_SLICE_INDEX(addr);
+ addr = (slice + 1) << SLICE_LOW_SHIFT;
+ if (!(available.low_slices & (1u << slice)))
+ continue;
+ } else {
+ slice = GET_HIGH_SLICE_INDEX(addr);
+ addr = (slice + 1) << SLICE_HIGH_SHIFT;
+ if (!(available.high_slices & (1u << slice)))
+ continue;
+ }
Into some kind of helper. It will probably compile to the same thing but
at least it's more readable and it will avoid a fuckup in the future if
somebody changes the algorithm and forgets to update one of the
copies :-)
Cheers,
Ben.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>