From 519f9845783bcbdbaace8d3d7f98e203d26bc411 Mon Sep 17 00:00:00 2001
From: Veselin Georgiev <anrieff@gmail.com>
Date: Mon, 5 Oct 2009 01:08:36 +0000
Subject: [PATCH] Added MPERF and APERF MSR incrementation speed calculation
 using a 10ms delay loop

git-svn-id: https://svn.code.sf.net/p/libcpuid/code/HEAD/libcpuid@75 3b4be424-7ac5-41d7-8526-f4ddcb85d872
---
 libcpuid/rdmsr.c | 30 ++++++++++++++++++++----------
 libcpuid/rdtsc.c | 23 +++++++++++++++++++++--
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/libcpuid/rdmsr.c b/libcpuid/rdmsr.c
index 2ea1790..3e823b3 100644
--- a/libcpuid/rdmsr.c
+++ b/libcpuid/rdmsr.c
@@ -358,6 +358,9 @@ int cpu_msr_driver_close(struct msr_driver_t* drv)
 
 #endif /* _WIN32 */
 
+ /* from rdtsc.c: */
+void sys_precise_clock(uint64_t *result);
+int busy_loop_delay(int milliseconds);
 
 static int rdmsr_supported(void)
 {
@@ -365,6 +368,21 @@ static int rdmsr_supported(void)
 	return id->flags[CPU_FEATURE_MSR];
 }
 
+static int perfmsr_measure(struct msr_driver_t* handle, int msr)
+{
+	int err;
+	uint64_t a, b;
+	uint64_t x, y;
+	err = cpu_rdmsr(handle, msr, &x);
+	if (err) return CPU_INVALID_VALUE;
+	sys_precise_clock(&a);
+	busy_loop_delay(10);
+	cpu_rdmsr(handle, msr, &y);
+	sys_precise_clock(&b);
+	if (a >= b || x > y) return CPU_INVALID_VALUE;
+	return (y - x) / (b - a);
+}
+
 int cpu_msrinfo(struct msr_driver_t* handle, cpu_msrinfo_request_t which)
 {
 	uint64_t r;
@@ -374,17 +392,9 @@ int cpu_msrinfo(struct msr_driver_t* handle, cpu_msrinfo_request_t which)
 		return set_error(ERR_HANDLE);
 	switch (which) {
 		case INFO_MPERF:
-		{
-			err = cpu_rdmsr(handle, 0xe7, &r);
-			if (err) return CPU_INVALID_VALUE;
-			return (int) (r & 0x7fffffff);
-		}
+			return perfmsr_measure(handle, 0xe7);
 		case INFO_APERF:
-		{
-			err = cpu_rdmsr(handle, 0xe8, &r);
-			if (err) return CPU_INVALID_VALUE;
-			return (int) (r & 0x7fffffff);
-		}
+			return perfmsr_measure(handle, 0xe8);
 		case INFO_CUR_MULTIPLIER:
 		{
 			err = cpu_rdmsr(handle, 0x2a, &r);
diff --git a/libcpuid/rdtsc.c b/libcpuid/rdtsc.c
index 2819a8e..2b098dd 100644
--- a/libcpuid/rdtsc.c
+++ b/libcpuid/rdtsc.c
@@ -29,7 +29,7 @@
 
 #ifdef _WIN32
 #include <windows.h>
-static void sys_precise_clock(uint64_t *result)
+void sys_precise_clock(uint64_t *result)
 {
 	double c, f;
 	LARGE_INTEGER freq, counter;
@@ -42,7 +42,7 @@ static void sys_precise_clock(uint64_t *result)
 #else
 /* assuming Linux, Mac OS or other POSIX */
 #include <sys/time.h>
-static void sys_precise_clock(uint64_t *result)
+void sys_precise_clock(uint64_t *result)
 {
 	struct timeval tv;
 	gettimeofday(&tv, NULL);
@@ -157,6 +157,25 @@ static int busy_loop(int amount)
 	return s;
 }
 
+int busy_loop_delay(int milliseconds)
+{
+	int cycles = 0, r = 0, first = 1;
+	uint64_t a, b, c;
+	sys_precise_clock(&a);
+	while (1) {
+		sys_precise_clock(&c);
+		if ((c - a) / 1000 > milliseconds) return r;
+		r += busy_loop(cycles);
+		if (first) {
+			first = 0;
+		} else {
+			if (c - b < 1000) cycles *= 2;
+			if (c - b > 10000) cycles /= 2;
+		}
+		b = c;
+	}
+}
+
 int cpu_clock_measure(int millis, int quad_check)
 {
 	struct cpu_mark_t begin[4], end[4], temp, temp2;