lkml.org 
[lkml]   [2006]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH] percpu data: only iterate over possible CPUs
    Date
    On Friday 10 February 2006 11:42, Andrew Morton wrote:
    > Andi Kleen <ak@muc.de> wrote:
    > >
    > > On Thursday 09 February 2006 19:04, Andrew Morton wrote:
    > > > Ashok Raj <ashok.raj@intel.com> wrote:
    > > > >
    > > > > The problem was with ACPI just simply looking at the namespace doesnt
    > > > > exactly give us an idea of how many processors are possible in this platform.
    > > >
    > > > We need to fix this asap - the performance penalty for HOTPLUG_CPU=y,
    > > > NR_CPUS=lots will be appreciable.
    > >
    > > What is this performance penalty exactly?
    >
    > All those for_each_cpu() loops will hit NR_CPUS cachelines instead of
    > hweight(cpu_possible_map) cachelines.

    But are there any in real fast paths? iirc they are mostly in initialization,
    where it doesn't matter too much.

    -Andi
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-02-10 13:15    [W:0.021 / U:90.652 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site