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    SubjectRe: [PATCH] slub: reduce overhead of slub_debug
    From
    On Thu, Jul 7, 2011 at 11:12 PM, Christoph Lameter <cl@linux.com> wrote:
    > On Thu, 7 Jul 2011, Pekka Enberg wrote:
    >
    >> I applied the patch. I think a follow up patch that moves the function
    >> to lib/string.c with proper generic name would be in order. Thanks!
    >
    > Well this is really straightforward. Hasnt seen much testing yet and
    > needs refinement but it would be like this:
    >
    >
    > ---
    >  arch/x86/include/asm/string_32.h |    2 ++
    >  arch/x86/lib/string_32.c         |   17 +++++++++++++++++
    >  include/linux/string.h           |    3 +++
    >  lib/string.c                     |   25 +++++++++++++++++++++++++
    >  mm/slub.c                        |   13 ++++++-------
    >  5 files changed, 53 insertions(+), 7 deletions(-)
    >
    > Index: linux-2.6/arch/x86/lib/string_32.c
    > ===================================================================
    > --- linux-2.6.orig/arch/x86/lib/string_32.c     2011-07-07 15:03:46.000000000 -0500
    > +++ linux-2.6/arch/x86/lib/string_32.c  2011-07-07 15:03:56.000000000 -0500
    > @@ -214,6 +214,23 @@ void *memscan(void *addr, int c, size_t
    >  EXPORT_SYMBOL(memscan);
    >  #endif
    >
    > +#ifdef __HAVE_ARCH_INV_MEMSCAN
    > +void *inv_memscan(void *addr, int c, size_t size)
    > +{
    > +       if (!size)
    > +               return addr;
    > +       asm volatile("repz; scasb\n\t"
    > +           "jz 1f\n\t"
    > +           "dec %%edi\n"
    > +           "1:"
    > +           : "=D" (addr), "=c" (size)
    > +           : "0" (addr), "1" (size), "a" (c)
    > +           : "memory");
    > +       return addr;
    > +}
    > +EXPORT_SYMBOL(memscan);
    > +#endif
    > +
    >  #ifdef __HAVE_ARCH_STRNLEN
    >  size_t strnlen(const char *s, size_t count)
    >  {
    > Index: linux-2.6/include/linux/string.h
    > ===================================================================
    > --- linux-2.6.orig/include/linux/string.h       2011-07-07 15:03:46.000000000 -0500
    > +++ linux-2.6/include/linux/string.h    2011-07-07 15:03:56.000000000 -0500
    > @@ -108,6 +108,9 @@ extern void * memmove(void *,const void
    >  #ifndef __HAVE_ARCH_MEMSCAN
    >  extern void * memscan(void *,int,__kernel_size_t);
    >  #endif
    > +#ifndef __HAVE_ARCH_INV_MEMSCAN
    > +extern void * inv_memscan(void *,int,__kernel_size_t);
    > +#endif
    >  #ifndef __HAVE_ARCH_MEMCMP
    >  extern int memcmp(const void *,const void *,__kernel_size_t);
    >  #endif
    > Index: linux-2.6/lib/string.c
    > ===================================================================
    > --- linux-2.6.orig/lib/string.c 2011-07-07 15:03:46.000000000 -0500
    > +++ linux-2.6/lib/string.c      2011-07-07 15:03:56.000000000 -0500
    > @@ -684,6 +684,31 @@ void *memscan(void *addr, int c, size_t
    >  EXPORT_SYMBOL(memscan);
    >  #endif
    >
    > +#ifndef __HAVE_ARCH_INV_MEMSCAN
    > +/**
    > + * memscan - Skip characters in an area of memory.
    > + * @addr: The memory area
    > + * @c: The byte to skip
    > + * @size: The size of the area.
    > + *
    > + * returns the address of the first mismatch of @c, or 1 byte past
    > + * the area if @c matches to the end
    > + */
    > +void *inv_memscan(void *addr, int c, size_t size)

    I think this needs a better name. My suggestion is memskip().
    --
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