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    SubjectRe: [PATCH 02/22 -v7] Add basic support for gcc profiler instrumentation
    Steven Rostedt wrote:

    > --- linux-mcount.git.orig/arch/x86/kernel/entry_32.S 2008-01-29 16:59:15.000000000 -0500
    > +++ linux-mcount.git/arch/x86/kernel/entry_32.S 2008-01-29 17:26:18.000000000 -0500
    > @@ -75,6 +75,31 @@ DF_MASK = 0x00000400
    > NT_MASK = 0x00004000
    > VM_MASK = 0x00020000
    >
    > +#ifdef CONFIG_MCOUNT
    > +.globl mcount
    > +mcount:
    > + /* unlikely(mcount_enabled) */
    > + cmpl $0, mcount_enabled
    > + jnz trace
    > + ret

    (and the corresponding 64-bit version)

    Is the impact of this change on the (already expensive) mcount_enabled
    case negligible? I worried about use cases where we want to gain some
    (relative) worst-case numbers via these instrumentations.

    In my personal priority scheme, CONFIG_MCOUNT=y && !mcount_enabled comes
    after mcount_enabled.

    Jan

    --
    Siemens AG, Corporate Technology, CT SE 2
    Corporate Competence Center Embedded Linux


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