lkml.org 
[lkml]   [2010]   [Jun]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 1/1] ARM: unwind - optimise linked-list searches for modules
    From
    Date
    On Tue, 2010-06-15 at 13:46 +0100, Phil Carmody wrote:
    > With several sections per module, and dozens of modules, the
    > searches down the linked list would dominate the lookup time,
    > dwarfing any savings from the binary search within the section.
    >
    > A simple move-to-front optimisation exploits the commonality
    > of the code paths taken, and in simple real-world tests reduces
    > the number of steps in the search to barely more than 1.
    >
    > Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
    > ---
    > arch/arm/kernel/unwind.c | 2 ++
    > 1 files changed, 2 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
    > index dd81a91..2e88abf 100644
    > --- a/arch/arm/kernel/unwind.c
    > +++ b/arch/arm/kernel/unwind.c
    > @@ -146,6 +146,8 @@ static struct unwind_idx *unwind_find_idx(unsigned long addr)
    > addr < table->end_addr) {
    > idx = search_index(addr, table->start,
    > table->stop - 1);
    > + /* MTF with 50 modules: 80 steps becomes ~1 */
    > + list_move(&table->list, &unwind_tables);

    That's a good optimisation. Could you please expand the "MTF" comment in
    the code a bit more? Otherwise,

    Acked-by: Catalin Marinas <catalin.marinas@arm.com>

    --
    Catalin



    \
     
     \ /
      Last update: 2010-06-25 19:21    [W:0.020 / U:0.168 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site