LXR linux-old/include/linux/prefetch.h

   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 <asm/processor.h>
  14#include <asm/cache.h>
  15
  16/*
  17        prefetch(x) attempts to pre-emptively get the memory pointed to
  18        by address "x" into the CPU L1 cache. 
  19        prefetch(x) should not cause any kind of exception, prefetch(0) is
  20        specifically ok.
  21
  22        prefetch() should be defined by the architecture, if not, the 
  23        #define below provides a no-op define.  
  24        
  25        There are 3 prefetch() macros:
  26        
  27        prefetch(x)     - prefetches the cacheline at "x" for read
  28        prefetchw(x)    - prefetches the cacheline at "x" for write
  29        spin_lock_prefetch(x) - prefectches the spinlock *x for taking
  30        
  31        there is also PREFETCH_STRIDE which is the architecure-prefered 
  32        "lookahead" size for prefetching streamed operations.
  33        
  34*/
  35
  36/*
  37 *      These cannot be do{}while(0) macros. See the mental gymnastics in
  38 *      the loop macro.
  39 */
  40 
  41#ifndef ARCH_HAS_PREFETCH
  42#define ARCH_HAS_PREFETCH
  43static inline void prefetch(const void *x) {;}
  44#endif
  45
  46#ifndef ARCH_HAS_PREFETCHW
  47#define ARCH_HAS_PREFETCHW
  48static inline void prefetchw(const void *x) {;}
  49#endif
  50
  51#ifndef ARCH_HAS_SPINLOCK_PREFETCH
  52#define ARCH_HAS_SPINLOCK_PREFETCH
  53#define spin_lock_prefetch(x) prefetchw(x)
  54#endif
  55
  56#ifndef PREFETCH_STRIDE
  57#define PREFETCH_STRIDE (4*L1_CACHE_BYTES)
  58#endif
  59
  60#endif
  61