lkml.org 
[lkml]   [2007]   [Dec]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: RFC: remove __read_mostly
    On Fri, Dec 14, 2007 at 04:38:04PM +0100, Eric Dumazet wrote:
    > Matt Mackall a ?crit :
    > >On Thu, Dec 13, 2007 at 11:20:44PM +0100, Adrian Bunk wrote:
    > >
    > >>I tried the following patch with a full x86 .config [1]:
    > >>
    > >>--- a/include/asm-x86/cache.h
    > >>+++ b/include/asm-x86/cache.h
    > >>-#define __read_mostly __attribute__((__section__(".data.read_mostly")))
    > >>+/* #define __read_mostly
    > >>__attribute__((__section__(".data.read_mostly"))) */
    > >>
    > >>The result [2,3] was:
    > >>
    > >>-rwxrwxr-x 1 bunk bunk 46607243 2007-12-13 19:50 vmlinux.old
    > >>-rwxrwxr-x 1 bunk bunk 46598691 2007-12-13 21:55 vmlinux
    > >>
    > >>It's not a surprise that the kernel can become bigger when __read_mostly
    > >>gets used, especially in cases where __read_mostly prevents gcc
    > >>optimizations.
    > >>
    > >>My question is:
    > >>Is there anywhere in the kernel a case where __read_mostly brings a
    > >>measurable improvement or can it be removed?
    > >>
    > >
    > >Yes, but perhaps we can put it under CONFIG_BASE_FULL?
    > >
    > >
    > Yes, we probably can do something like that (in addition to !CONFIG_SMP)

    Excellent point. If either CONFIG_BASE_FULL or CONFIG_SMP are not set,
    we should not define __read_mostly.

    --
    Mathematics is the supreme nostalgia of our time.


    \
     
     \ /
      Last update: 2007-12-14 16:47    [W:0.036 / U:4.324 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site