path: root/sysdeps/x86_64/cacheinfo.c

/* x86_64 cache info.
   Copyright (C) 2003, 2004, 2006, 2007, 2009 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.
*/

#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <cpuid.h>

#ifndef __cpuid_count
/* FIXME: Provide __cpuid_count if it isn't defined.  Copied from gcc
   4.4.0.  Remove this if gcc 4.4 is the minimum requirement.  */
# if defined(__i386__) && defined(__PIC__)
/* %ebx may be the PIC register.  */
#  define __cpuid_count(level, count, a, b, c, d)		\
  __asm__ ("xchg{l}\t{%%}ebx, %1\n\t"			\
	   "cpuid\n\t"					\
	   "xchg{l}\t{%%}ebx, %1\n\t"			\
	   : "=a" (a), "=r" (b), "=c" (c), "=d" (d)	\
	   : "0" (level), "2" (count))
# else
#  define __cpuid_count(level, count, a, b, c, d)		\
  __asm__ ("cpuid\n\t"					\
	   : "=a" (a), "=b" (b), "=c" (c), "=d" (d)	\
	   : "0" (level), "2" (count))
# endif
#endif

#ifdef USE_MULTIARCH
# include "multiarch/init-arch.h"

# define is_intel __cpu_features.kind == arch_kind_intel
# define is_amd __cpu_features.kind == arch_kind_amd
# define max_cpuid __cpu_features.max_cpuid
#else
  /* This spells out "GenuineIntel".  */
# define is_intel \
  ebx == 0x756e6547 && ecx == 0x6c65746e && edx == 0x49656e69
  /* This spells out "AuthenticAMD".  */
# define is_amd \
  ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65
#endif

static const struct intel_02_cache_info
{
  unsigned char idx;
  unsigned char assoc;
  unsigned char linesize;
  unsigned char rel_name;
  unsigned int size;
} intel_02_known [] =
  {
#define M(sc) ((sc) - _SC_LEVEL1_ICACHE_SIZE)
    { 0x06,  4, 32, M(_SC_LEVEL1_ICACHE_SIZE),    8192 },
    { 0x08,  4, 32, M(_SC_LEVEL1_ICACHE_SIZE),   16384 },
    { 0x09,  4, 32, M(_SC_LEVEL1_ICACHE_SIZE),   32768 },
    { 0x0a,  2, 32, M(_SC_LEVEL1_DCACHE_SIZE),    8192 },
    { 0x0c,  4, 32, M(_SC_LEVEL1_DCACHE_SIZE),   16384 },
    { 0x0d,  4, 64, M(_SC_LEVEL1_DCACHE_SIZE),   16384 },
    { 0x21,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),   262144 },
    { 0x22,  4, 64, M(_SC_LEVEL3_CACHE_SIZE),   524288 },
    { 0x23,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  1048576 },
    { 0x25,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  2097152 },
    { 0x29,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  4194304 },
    { 0x2c,  8, 64, M(_SC_LEVEL1_DCACHE_SIZE),   32768 },
    { 0x30,  8, 64, M(_SC_LEVEL1_ICACHE_SIZE),   32768 },
    { 0x39,  4, 64, M(_SC_LEVEL2_CACHE_SIZE),   131072 },
    { 0x3a,  6, 64, M(_SC_LEVEL2_CACHE_SIZE),   196608 },
    { 0x3b,  2, 64, M(_SC_LEVEL2_CACHE_SIZE),   131072 },
    { 0x3c,  4, 64, M(_SC_LEVEL2_CACHE_SIZE),   262144 },
    { 0x3d,  6, 64, M(_SC_LEVEL2_CACHE_SIZE),   393216 },
    { 0x3e,  4, 64, M(_SC_LEVEL2_CACHE_SIZE),   524288 },
    { 0x3f,  2, 64, M(_SC_LEVEL2_CACHE_SIZE),   262144 },
    { 0x41,  4, 32, M(_SC_LEVEL2_CACHE_SIZE),   131072 },
    { 0x42,  4, 32, M(_SC_LEVEL2_CACHE_SIZE),   262144 },
    { 0x43,  4, 32, M(_SC_LEVEL2_CACHE_SIZE),   524288 },
    { 0x44,  4, 32, M(_SC_LEVEL2_CACHE_SIZE),  1048576 },
    { 0x45,  4, 32, M(_SC_LEVEL2_CACHE_SIZE),  2097152 },
    { 0x46,  4, 64, M(_SC_LEVEL3_CACHE_SIZE),  4194304 },
    { 0x47,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  8388608 },
    { 0x48, 12, 64, M(_SC_LEVEL2_CACHE_SIZE),  3145728 },
    { 0x49, 16, 64, M(_SC_LEVEL2_CACHE_SIZE),  4194304 },
    { 0x4a, 12, 64, M(_SC_LEVEL3_CACHE_SIZE),  6291456 },
    { 0x4b, 16, 64, M(_SC_LEVEL3_CACHE_SIZE),  8388608 },
    { 0x4c, 12, 64, M(_SC_LEVEL3_CACHE_SIZE), 12582912 },
    { 0x4d, 16, 64, M(_SC_LEVEL3_CACHE_SIZE), 16777216 },
    { 0x4e, 24, 64, M(_SC_LEVEL2_CACHE_SIZE),  6291456 },
    { 0x60,  8, 64, M(_SC_LEVEL1_DCACHE_SIZE),   16384 },
    { 0x66,  4, 64, M(_SC_LEVEL1_DCACHE_SIZE),    8192 },
    { 0x67,  4, 64, M(_SC_LEVEL1_DCACHE_SIZE),   16384 },
    { 0x68,  4, 64, M(_SC_LEVEL1_DCACHE_SIZE),   32768 },
    { 0x78,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),  1048576 },
    { 0x79,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),   131072 },
    { 0x7a,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),   262144 },
    { 0x7b,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),   524288 },
    { 0x7c,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),  1048576 },
    { 0x7d,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),  2097152 },
    { 0x7f,  2, 64, M(_SC_LEVEL2_CACHE_SIZE),   524288 },
    { 0x82,  8, 32, M(_SC_LEVEL2_CACHE_SIZE),   262144 },
    { 0x83,  8, 32, M(_SC_LEVEL2_CACHE_SIZE),   524288 },
    { 0x84,  8, 32, M(_SC_LEVEL2_CACHE_SIZE),  1048576 },
    { 0x85,  8, 32, M(_SC_LEVEL2_CACHE_SIZE),  2097152 },
    { 0x86,  4, 64, M(_SC_LEVEL2_CACHE_SIZE),   524288 },
    { 0x87,  8, 64, M(_SC_LEVEL2_CACHE_SIZE),  1048576 },
    { 0xd0,  4, 64, M(_SC_LEVEL3_CACHE_SIZE),   524288 },
    { 0xd1,  4, 64, M(_SC_LEVEL3_CACHE_SIZE),  1048576 },
    { 0xd2,  4, 64, M(_SC_LEVEL3_CACHE_SIZE),  2097152 },
    { 0xd6,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  1048576 },
    { 0xd7,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  2097152 },
    { 0xd8,  8, 64, M(_SC_LEVEL3_CACHE_SIZE),  4194304 },
    { 0xdc, 12, 64, M(_SC_LEVEL3_CACHE_SIZE),  2097152 },
    { 0xdd, 12, 64, M(_SC_LEVEL3_CACHE_SIZE),  4194304 },
    { 0xde, 12, 64, M(_SC_LEVEL3_CACHE_SIZE),  8388608 },
    { 0xe3, 16, 64, M(_SC_LEVEL3_CACHE_SIZE),  2097152 },
    { 0xe3, 16, 64, M(_SC_LEVEL3_CACHE_SIZE),  4194304 },
    { 0xe4, 16, 64, M(_SC_LEVEL3_CACHE_SIZE),  8388608 },
    { 0xea, 24, 64, M(_SC_LEVEL3_CACHE_SIZE), 12582912 },
    { 0xeb, 24, 64, M(_SC_LEVEL3_CACHE_SIZE), 18874368 },
    { 0xec, 24, 64, M(_SC_LEVEL3_CACHE_SIZE), 25165824 },
  };

#define nintel_02_known (sizeof (intel_02_known) / sizeof (intel_02_known [0]))

static int
intel_02_known_compare (const void *p1, const void *p2)
{
  const struct intel_02_cache_info *i1;
  const struct intel_02_cache_info *i2;

  i1 = (const struct intel_02_cache_info *) p1;
  i2 = (const struct intel_02_cache_info *) p2;

  if (i1->idx == i2->idx)
    return 0;

  return i1->idx < i2->idx ? -1 : 1;
}


static long int
__attribute__ ((noinline))
intel_check_word (int name, unsigned int value, bool *has_level_2,
		  bool *no_level_2_or_3)
{
  if ((value & 0x80000000) != 0)
    /* The register value is reserved.  */
    return 0;

  /* Fold the name.  The _SC_ constants are always in the order SIZE,
     ASSOC, LINESIZE.  */
  int folded_rel_name = (M(name) / 3) * 3;

  while (value != 0)
    {
      unsigned int byte = value & 0xff;

      if (byte == 0x40)
	{
	  *no_level_2_or_3 = true;

	  if (folded_rel_name == M(_SC_LEVEL3_CACHE_SIZE))
	    /* No need to look further.  */
	    break;
	}
      else
	{
	  if (byte == 0x49 && folded_rel_name == M(_SC_LEVEL3_CACHE_SIZE))
	    {
	      /* Intel reused this value.  For family 15, model 6 it
		 specifies the 3rd level cache.  Otherwise the 2nd
		 level cache.  */
	      unsigned int family;
	      unsigned int model;
#ifdef USE_MULTIARCH
	      family = __cpu_features.family;
	      model = __cpu_features.model;
#else
	      unsigned int eax;
	      unsigned int ebx;
	      unsigned int ecx;
	      unsigned int edx;
	      __cpuid (1, eax, ebx, ecx, edx);

	      family = ((eax >> 20) & 0xff) + ((eax >> 8) & 0xf);
	      model = (((eax >>16) & 0xf) << 4) + ((eax >> 4) & 0xf);
#endif

	      if (family == 15 && model == 6)
		{
		  /* The level 3 cache is encoded for this model like
		     the level 2 cache is for other models.  Pretend
		     the caller asked for the level 2 cache.  */
		  name = (_SC_LEVEL2_CACHE_SIZE
			  + (name - _SC_LEVEL3_CACHE_SIZE));
		  folded_rel_name = M(_SC_LEVEL2_CACHE_SIZE);
		}
	    }

	  struct intel_02_cache_info *found;
	  struct intel_02_cache_info search;

	  search.idx = byte;
	  found = bsearch (&search, intel_02_known, nintel_02_known,
			   sizeof (intel_02_known[0]), intel_02_known_compare);
	  if (found != NULL)
	    {
	      if (found->rel_name == folded_rel_name)
		{
		  unsigned int offset = M(name) - folded_rel_name;

		  if (offset == 0)
		    /* Cache size.  */
		    return found->size;
		  if (offset == 1)
		    return found->assoc;

		  assert (offset == 2);
		  return found->linesize;
		}

	      if (found->rel_name == M(_SC_LEVEL2_CACHE_SIZE))
		*has_level_2 = true;
	    }
	}

      /* Next byte for the next round.  */
      value >>= 8;
    }

  /* Nothing found.  */
  return 0;
}


static long int __attribute__ ((noinline))
handle_intel (int name, unsigned int maxidx)
{
  assert (maxidx >= 2);

  /* OK, we can use the CPUID instruction to get all info about the
     caches.  */
  unsigned int cnt = 0;
  unsigned int max = 1;
  long int result = 0;
  bool no_level_2_or_3 = false;
  bool has_level_2 = false;

  while (cnt++ < max)
    {
      unsigned int eax;
      unsigned int ebx;
      unsigned int ecx;
      unsigned int edx;
      __cpuid (2, eax, ebx, ecx, edx);

      /* The low byte of EAX in the first round contain the number of
	 rounds we have to make.  At least one, the one we are already
	 doing.  */
      if (cnt == 1)
	{
	  max = eax & 0xff;
	  eax &= 0xffffff00;
	}

      /* Process the individual registers' value.  */
      result = intel_check_word (name, eax, &has_level_2, &no_level_2_or_3);
      if (result != 0)
	return result;

      result = intel_check_word (name, ebx, &has_level_2, &no_level_2_or_3);
      if (result != 0)
	return result;

      result = intel_check_word (name, ecx, &has_level_2, &no_level_2_or_3);
      if (result != 0)
	return result;

      result = intel_check_word (name, edx, &has_level_2, &no_level_2_or_3);
      if (result != 0)
	return result;
    }

  if (name >= _SC_LEVEL2_CACHE_SIZE && name <= _SC_LEVEL3_CACHE_LINESIZE
      && no_level_2_or_3)
    return -1;

  return 0;
}


static long int __attribute__ ((noinline))
handle_amd (int name)
{
  unsigned int eax;
  unsigned int ebx;
  unsigned int ecx;
  unsigned int edx;
  __cpuid (0x80000000, eax, ebx, ecx, edx);

  /* No level 4 cache (yet).  */
  if (name > _SC_LEVEL3_CACHE_LINESIZE)
    return 0;

  unsigned int fn = 0x80000005 + (name >= _SC_LEVEL2_CACHE_SIZE);
  if (eax < fn)
    return 0;

  __cpuid (fn, eax, ebx, ecx, edx);

  if (name < _SC_LEVEL1_DCACHE_SIZE)
    {
      name += _SC_LEVEL1_DCACHE_SIZE - _SC_LEVEL1_ICACHE_SIZE;
      ecx = edx;
    }

  switch (name)
    {
    case _SC_LEVEL1_DCACHE_SIZE:
      return (ecx >> 14) & 0x3fc00;

    case _SC_LEVEL1_DCACHE_ASSOC:
      ecx >>= 16;
      if ((ecx & 0xff) == 0xff)
	/* Fully associative.  */
	return (ecx << 2) & 0x3fc00;
      return ecx & 0xff;

    case _SC_LEVEL1_DCACHE_LINESIZE:
      return ecx & 0xff;

    case _SC_LEVEL2_CACHE_SIZE:
      return (ecx & 0xf000) == 0 ? 0 : (ecx >> 6) & 0x3fffc00;

    case _SC_LEVEL2_CACHE_ASSOC:
      switch ((ecx >> 12) & 0xf)
        {
        case 0:
        case 1:
        case 2:
        case 4:
	  return (ecx >> 12) & 0xf;
	case 6:
	  return 8;
	case 8:
	  return 16;
	case 10:
	  return 32;
	case 11:
	  return 48;
	case 12:
	  return 64;
	case 13:
	  return 96;
	case 14:
	  return 128;
	case 15:
	  return ((ecx >> 6) & 0x3fffc00) / (ecx & 0xff);
	default:
	  return 0;
        }
      /* NOTREACHED */

    case _SC_LEVEL2_CACHE_LINESIZE:
      return (ecx & 0xf000) == 0 ? 0 : ecx & 0xff;

    case _SC_LEVEL3_CACHE_SIZE:
      return (edx & 0xf000) == 0 ? 0 : (edx & 0x3ffc0000) << 1;

    case _SC_LEVEL3_CACHE_ASSOC:
      switch ((edx >> 12) & 0xf)
	{
	case 0:
	case 1:
	case 2:
	case 4:
	  return (edx >> 12) & 0xf;
	case 6:
	  return 8;
	case 8:
	  return 16;
	case 10:
	  return 32;
	case 11:
	  return 48;
	case 12:
	  return 64;
	case 13:
	  return 96;
	case 14:
	  return 128;
	case 15:
	  return ((edx & 0x3ffc0000) << 1) / (edx & 0xff);
	default:
	  return 0;
	}
      /* NOTREACHED */

    case _SC_LEVEL3_CACHE_LINESIZE:
      return (edx & 0xf000) == 0 ? 0 : edx & 0xff;

    default:
      assert (! "cannot happen");
    }
  return -1;
}


/* Get the value of the system variable NAME.  */
long int
attribute_hidden
__cache_sysconf (int name)
{
#ifdef USE_MULTIARCH
  if (__cpu_features.kind == arch_kind_unknown)
    __init_cpu_features ();
#else
  /* Find out what brand of processor.  */
  unsigned int max_cpuid;
  unsigned int ebx;
  unsigned int ecx;
  unsigned int edx;
  __cpuid (0, max_cpuid, ebx, ecx, edx);
#endif

  if (is_intel)
    return handle_intel (name, max_cpuid);

  if (is_amd)
    return handle_amd (name);

  // XXX Fill in more vendors.

  /* CPU not known, we have no information.  */
  return 0;
}


/* Half the data cache size for use in memory and string routines, typically
   L1 size.  */
long int __x86_64_data_cache_size_half attribute_hidden = 32 * 1024 / 2;
/* Shared cache size for use in memory and string routines, typically
   L2 or L3 size.  */
long int __x86_64_shared_cache_size_half attribute_hidden = 1024 * 1024 / 2;
long int __x86_64_shared_cache_size attribute_hidden = 1024 * 1024;

#ifndef DISABLE_PREFETCHW
/* PREFETCHW support flag for use in memory and string routines.  */
int __x86_64_prefetchw attribute_hidden;
#endif

#ifndef DISABLE_PREFERRED_MEMORY_INSTRUCTION
/* Instructions preferred for memory and string routines.

  0: Regular instructions
  1: MMX instructions
  2: SSE2 instructions
  3: SSSE3 instructions

  */
int __x86_64_preferred_memory_instruction attribute_hidden;
#endif


static void
__attribute__((constructor))
init_cacheinfo (void)
{
  /* Find out what brand of processor.  */
  unsigned int eax;
  unsigned int ebx;
  unsigned int ecx;
  unsigned int edx;
  int max_cpuid_ex;
  long int data = -1;
  long int shared = -1;
  unsigned int level;
  unsigned int threads = 0;

#ifdef USE_MULTIARCH
  if (__cpu_features.kind == arch_kind_unknown)
    __init_cpu_features ();
#else
  int max_cpuid;
  __cpuid (0, max_cpuid, ebx, ecx, edx);
#endif

  if (is_intel)
    {
      data = handle_intel (_SC_LEVEL1_DCACHE_SIZE, max_cpuid);

      /* Try L3 first.  */
      level  = 3;
      shared = handle_intel (_SC_LEVEL3_CACHE_SIZE, max_cpuid);

      if (shared <= 0)
        {
	  /* Try L2 otherwise.  */
          level  = 2;
          shared = handle_intel (_SC_LEVEL2_CACHE_SIZE, max_cpuid);
	}

      unsigned int ebx_1;

#ifdef USE_MULTIARCH
      eax = __cpu_features.cpuid[COMMON_CPUID_INDEX_1].eax;
      ebx_1 = __cpu_features.cpuid[COMMON_CPUID_INDEX_1].ebx;
      ecx = __cpu_features.cpuid[COMMON_CPUID_INDEX_1].ecx;
      edx = __cpu_features.cpuid[COMMON_CPUID_INDEX_1].edx;
#else
      __cpuid (1, eax, ebx_1, ecx, edx);
#endif

#ifndef DISABLE_PREFERRED_MEMORY_INSTRUCTION
      /* Intel prefers SSSE3 instructions for memory/string routines
	 if they are avaiable.  */
      if ((ecx & 0x200))
	__x86_64_preferred_memory_instruction = 3;
      else
	__x86_64_preferred_memory_instruction = 2;
#endif

      /* Figure out the number of logical threads that share the
	 highest cache level.  */
      if (max_cpuid >= 4)
        {
	  int i = 0;

	  /* Query until desired cache level is enumerated.  */
	  do
	    {
	      __cpuid_count (4, i++, eax, ebx, ecx, edx);

	      /* There seems to be a bug in at least some Pentium Ds
		 which sometimes fail to iterate all cache parameters.
		 Do not loop indefinitely here, stop in this case and
		 assume there is no such information.  */
	      if ((eax & 0x1f) == 0)
		goto intel_bug_no_cache_info;
	    }
          while (((eax >> 5) & 0x7) != level);

	  threads = (eax >> 14) & 0x3ff;
	
	  /* If max_cpuid >= 11, THREADS is the maximum number of
	      addressable IDs for logical processors sharing the
	      cache, instead of the maximum number of threads
	      sharing the cache.  */
	  if (threads && max_cpuid >= 11)
	    {
	      /* Find the number of logical processors shipped in
		 one core and apply count mask.  */
	      i = 0;
	      while (1)
		{
		  __cpuid_count (11, i++, eax, ebx, ecx, edx);

		  int shipped = ebx & 0xff;
		  int type = ecx & 0xff0;
		  if (shipped == 0 || type == 0)
		    break;
		  else if (type == 0x200)
		    {
		      int count_mask;

		      /* Compute count mask.  */
		      asm ("bsr %1, %0"
			   : "=r" (count_mask) : "g" (threads));
		      count_mask = ~(-1 << (count_mask + 1));
		      threads = (shipped - 1) & count_mask;
		      break;
		    }
		}
	    }
	  threads += 1;
	}
      else
        {
	intel_bug_no_cache_info:
	  /* Assume that all logical threads share the highest cache level.  */

	  threads = (ebx_1 >> 16) & 0xff;
	}

      /* Cap usage of highest cache level to the number of supported
	 threads.  */
      if (shared > 0 && threads > 0)
        shared /= threads;
    }
  /* This spells out "AuthenticAMD".  */
  else if (is_amd)
    {
      data   = handle_amd (_SC_LEVEL1_DCACHE_SIZE);
      long int core = handle_amd (_SC_LEVEL2_CACHE_SIZE);
      shared = handle_amd (_SC_LEVEL3_CACHE_SIZE);

      /* Get maximum extended function. */
      __cpuid (0x80000000, max_cpuid_ex, ebx, ecx, edx);

      if (shared <= 0)
	/* No shared L3 cache.  All we have is the L2 cache.  */
	shared = core;
      else
	{
	  /* Figure out the number of logical threads that share L3.  */
	  if (max_cpuid_ex >= 0x80000008)
	    {
	      /* Get width of APIC ID.  */
	      __cpuid (0x80000008, max_cpuid_ex, ebx, ecx, edx);
	      threads = 1 << ((ecx >> 12) & 0x0f);
	    }

	  if (threads == 0)
	    {
	      /* If APIC ID width is not available, use logical
		 processor count.  */
	      __cpuid (0x00000001, max_cpuid_ex, ebx, ecx, edx);

	      if ((edx & (1 << 28)) != 0)
		threads = (ebx >> 16) & 0xff;
	    }

	  /* Cap usage of highest cache level to the number of
	     supported threads.  */
	  if (threads > 0)
	    shared /= threads;

	  /* Account for exclusive L2 and L3 caches.  */
	  shared += core;
	}

#ifndef DISABLE_PREFETCHW
      if (max_cpuid_ex >= 0x80000001)
	{
	  __cpuid (0x80000001, eax, ebx, ecx, edx);
	  /*  PREFETCHW     || 3DNow!  */
	  if ((ecx & 0x100) || (edx & 0x80000000))
	    __x86_64_prefetchw = -1;
	}
#endif
    }

  if (data > 0)
    __x86_64_data_cache_size_half = data / 2;

  if (shared > 0)
    {
      __x86_64_shared_cache_size_half = shared / 2;
      __x86_64_shared_cache_size = shared;
    }
}