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 <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) - prefectches the spinlock *x for taking
  31
  32         there is also PREFETCH_STRIDE which is the architecure-prefered
  33         "lookahead" size for prefetching streamed operations.
  34
  35 */
  36
  37 /*
  38  *      These cannot be do{}while(0) macros. See the mental gymnastics in
  39  *      the loop macro.
  40  */
  41
  42 #ifndef ARCH_HAS_PREFETCH
  43 static inline void prefetch(const void *x) {;}
  44 #endif
  45
  46 #ifndef ARCH_HAS_PREFETCHW
  47 static inline void prefetchw(const void *x) {;}
  48 #endif
  49
  50 #ifndef ARCH_HAS_SPINLOCK_PREFETCH
  51 #define spin_lock_prefetch(x) prefetchw(x)
  52 #endif
  53
  54 #ifndef PREFETCH_STRIDE
  55 #define PREFETCH_STRIDE (4*L1_CACHE_BYTES)
  56 #endif
  57
  58 static inline void prefetch_range(void *addr, size_t len)
  59 {
  60 #ifdef ARCH_HAS_PREFETCH
  61         char *cp;
  62         char *end = addr + len;
  63
  64         for (cp = addr; cp < end; cp += PREFETCH_STRIDE)
  65                 prefetch(cp);
  66 #endif
  67 }
  68
  69 #endif