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    SubjectRe: [PATCH 1/2] function-graph: disable when both x86_32 and optimize for size are configured

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > On Sat, 20 Jun 2009, Ingo Molnar wrote:
    >
    > >
    > > * Steven Rostedt <rostedt@goodmis.org> wrote:
    > >
    > > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
    > > > index 4a13e5a..1eac852 100644
    > > > --- a/kernel/trace/Kconfig
    > > > +++ b/kernel/trace/Kconfig
    > > > @@ -121,6 +121,7 @@ config FUNCTION_GRAPH_TRACER
    > > > bool "Kernel Function Graph Tracer"
    > > > depends on HAVE_FUNCTION_GRAPH_TRACER
    > > > depends on FUNCTION_TRACER
    > > > + depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
    > > > default y
    > >
    > > Hm, nice fix, but this is a quite nasty constraint - distros like to
    > > enable CC_OPTIMIZE_FOR_SIZE as it neatly trims the kernel's size by
    > > about 30%.
    > >
    > > Just in case you have not checked yet: is there no way to turn off
    > > the specific gcc optimization that causes this? Or is it -Os itself
    > > that does this optimization?
    >
    > It seems to me that -Os causes it for i386. I did a make V=1 to
    > capture how the files in question were being compiled, and tried
    > various disabling of flags. -Os was the only one to make a
    > difference. :-(

    oh well. I think GCC should be fixed/improved to not do this
    particular (rather narrow looking) optimization if -pg is specified
    too.

    Ingo


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