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    SubjectRe: [PATCH 2/4] generic-smp: remove kmalloc usage
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    On Thu, 2009-02-19 at 15:01 +1030, Rusty Russell wrote:
    > On Thursday 19 February 2009 02:35:35 Ingo Molnar wrote:
    > >
    > > * Rusty Russell <rusty@rustcorp.com.au> wrote:
    > >
    > > > On Tuesday 17 February 2009 20:13:59 Ingo Molnar wrote:
    > > > > We should not bend backwards trying to preserve that kmalloc()
    > > > > [and prove that it's safe and race-free] - i.e. the burden of
    > > > > proof is on the person insisting that it's needed, not on the
    > > > > person wanting to remove it.
    > > >
    > > > Respectfully disagree. The kmalloc has been there for a very long time,
    > > > and doing fine AFAICT.
    > >
    > > The kmalloc(GFP_ATOMIC) has been in kernel/smp.c for about half
    > > a year
    >
    > Oops, yes.
    >
    > So if we care about the kmalloc, why didn't we see benchmarks when we
    > switched from the x86 smp_call_function_mask to the generic one? Or did
    > I just miss them (there's nothing in the git commit).
    >
    > Now, I think the current patch is quite neat and may not been benchmarks to
    > justify it, but it'd still be nice if it were faster, but noone seems to know.

    I think the problem is that even on a lively machine these routines just
    aren't called that often:

    CAL: 74 104 93 116 Function call interrupts
    make clean; make -j8 bzImage
    CAL: 74 104 93 116 Function call interrupts

    We could of course construct some artificial ubench to stress it...



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