On Tue, Jan 8, 2013 at 6:15 PM, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 2013-01-08 at 17:28 -0800, Michel Lespinasse wrote: >> Update the powerpc slice_get_unmapped_area function to make use of >> vm_unmapped_area() instead of implementing a brute force search. >> >> Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx> >> >> --- >> arch/powerpc/mm/slice.c | 128 +++++++++++++++++++++++++++++----------------- >> 1 files changed, 81 insertions(+), 47 deletions(-) > > That doesn't look good ... the resulting code is longer than the > original, which makes me wonder how it is an improvement... 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. -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies. -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
