Messages in this thread |  | | Subject | Re: [PATCH 7/8] mm: use vm_unmapped_area() on powerpc architecture | From | Benjamin Herrenschmidt <> | Date | Wed, 09 Jan 2013 14:32:56 +1100 |
| |
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.
|  |