linux/include/linux/prefetch.h
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   1/*
   2 *  Generic cache management functions. Everything is arch-specific,  
   3 *  but this header exists to make sure the defines/functions can be
   4 *  used in a generic way.
   5 *
   6 *  2000-11-13  Arjan van de Ven   <arjan@fenrus.demon.nl>
   7 *
   8 */
   9
  10#ifndef _LINUX_PREFETCH_H
  11#define _LINUX_PREFETCH_H
  12
  13#include <linux/types.h>
  14#include <asm/processor.h>
  15#include <asm/cache.h>
  16
  17/*
  18        prefetch(x) attempts to pre-emptively get the memory pointed to
  19        by address "x" into the CPU L1 cache. 
  20        prefetch(x) should not cause any kind of exception, prefetch(0) is
  21        specifically ok.
  22
  23        prefetch() should be defined by the architecture, if not, the 
  24        #define below provides a no-op define.  
  25        
  26        There are 3 prefetch() macros:
  27        
  28        prefetch(x)     - prefetches the cacheline at "x" for read
  29        prefetchw(x)    - prefetches the cacheline at "x" for write
  30        spin_lock_prefetch(x) - prefetches the spinlock *x for taking
  31        
  32        there is also PREFETCH_STRIDE which is the architecure-preferred 
  33        "lookahead" size for prefetching streamed operations.
  34        
  35*/
  36
  37#ifndef ARCH_HAS_PREFETCH
  38#define prefetch(x) __builtin_prefetch(x)
  39#endif
  40
  41#ifndef ARCH_HAS_PREFETCHW
  42#define prefetchw(x) __builtin_prefetch(x,1)
  43#endif
  44
  45#ifndef ARCH_HAS_SPINLOCK_PREFETCH
  46#define spin_lock_prefetch(x) prefetchw(x)
  47#endif
  48
  49#ifndef PREFETCH_STRIDE
  50#define PREFETCH_STRIDE (4*L1_CACHE_BYTES)
  51#endif
  52
  53static inline void prefetch_range(void *addr, size_t len)
  54{
  55#ifdef ARCH_HAS_PREFETCH
  56        char *cp;
  57        char *end = addr + len;
  58
  59        for (cp = addr; cp < end; cp += PREFETCH_STRIDE)
  60                prefetch(cp);
  61#endif
  62}
  63
  64#endif
  65
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