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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 <[email protected]>
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 
53 static 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