From: Pierre-Marc Fournier <pierre-marc.fournier@polymtl.ca>
Date: Sat, 7 Feb 2009 07:11:22 +0000 (-0500)
Subject: ust: add kernel prefetch.h
X-Git-Tag: v0.1~310
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=7557eb6adb6b5bec85491f6edd5775201a37a8eb;p=ust.git

ust: add kernel prefetch.h
---

diff --git a/libmarkers/prefetch.h b/libmarkers/prefetch.h
new file mode 100644
index 0000000..af7c36a
--- /dev/null
+++ b/libmarkers/prefetch.h
@@ -0,0 +1,64 @@
+/*
+ *  Generic cache management functions. Everything is arch-specific,  
+ *  but this header exists to make sure the defines/functions can be
+ *  used in a generic way.
+ *
+ *  2000-11-13  Arjan van de Ven   <arjan@fenrus.demon.nl>
+ *
+ */
+
+#ifndef _LINUX_PREFETCH_H
+#define _LINUX_PREFETCH_H
+
+#include <linux/types.h>
+#include <asm/processor.h>
+#include <asm/cache.h>
+
+/*
+	prefetch(x) attempts to pre-emptively get the memory pointed to
+	by address "x" into the CPU L1 cache. 
+	prefetch(x) should not cause any kind of exception, prefetch(0) is
+	specifically ok.
+
+	prefetch() should be defined by the architecture, if not, the 
+	#define below provides a no-op define.	
+	
+	There are 3 prefetch() macros:
+	
+	prefetch(x)  	- prefetches the cacheline at "x" for read
+	prefetchw(x)	- prefetches the cacheline at "x" for write
+	spin_lock_prefetch(x) - prefetches the spinlock *x for taking
+	
+	there is also PREFETCH_STRIDE which is the architecure-prefered 
+	"lookahead" size for prefetching streamed operations.
+	
+*/
+
+#ifndef ARCH_HAS_PREFETCH
+#define prefetch(x) __builtin_prefetch(x)
+#endif
+
+#ifndef ARCH_HAS_PREFETCHW
+#define prefetchw(x) __builtin_prefetch(x,1)
+#endif
+
+#ifndef ARCH_HAS_SPINLOCK_PREFETCH
+#define spin_lock_prefetch(x) prefetchw(x)
+#endif
+
+#ifndef PREFETCH_STRIDE
+#define PREFETCH_STRIDE (4*L1_CACHE_BYTES)
+#endif
+
+static inline void prefetch_range(void *addr, size_t len)
+{
+#ifdef ARCH_HAS_PREFETCH
+	char *cp;
+	char *end = addr + len;
+
+	for (cp = addr; cp < end; cp += PREFETCH_STRIDE)
+		prefetch(cp);
+#endif
+}
+
+#endif