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    SubjectRe: [PATCH 3/3] x86: add local_tlb_flush_kernel_range()
    From
    On Mon, Jun 25, 2012 at 12:14 PM, Seth Jennings
    <sjenning@linux.vnet.ibm.com> wrote:
    > This patch adds support for a local_tlb_flush_kernel_range()
    > function for the x86 arch.  This function allows for CPU-local
    > TLB flushing, potentially using invlpg for single entry flushing,
    > using an arch independent function name.

    What x86 hardware did you use to figure the optimal number?

    >
    > Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
    > ---
    >  arch/x86/include/asm/tlbflush.h |   21 +++++++++++++++++++++
    >  1 file changed, 21 insertions(+)
    >
    > diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
    > index 36a1a2a..92a280b 100644
    > --- a/arch/x86/include/asm/tlbflush.h
    > +++ b/arch/x86/include/asm/tlbflush.h
    > @@ -168,4 +168,25 @@ static inline void flush_tlb_kernel_range(unsigned long start,
    >        flush_tlb_all();
    >  }
    >
    > +#define __HAVE_LOCAL_FLUSH_TLB_KERNEL_RANGE
    > +/*
    > + * INVLPG_BREAK_EVEN_PAGES is the number of pages after which single tlb
    > + * flushing becomes more costly than just doing a complete tlb flush.
    > + * While this break even point varies among x86 hardware, tests have shown
    > + * that 8 is a good generic value.
    > +*/
    > +#define INVLPG_BREAK_EVEN_PAGES 8
    > +static inline void local_flush_tlb_kernel_range(unsigned long start,
    > +               unsigned long end)
    > +{
    > +       if (cpu_has_invlpg &&
    > +               (end - start)/PAGE_SIZE <= INVLPG_BREAK_EVEN_PAGES) {
    > +               while (start < end) {
    > +                       __flush_tlb_single(start);
    > +                       start += PAGE_SIZE;
    > +               }
    > +       } else
    > +               local_flush_tlb();
    > +}
    > +
    >  #endif /* _ASM_X86_TLBFLUSH_H */
    > --
    > 1.7.9.5
    >
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