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-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 70