linux-kernel - [RFC PATCH 2/9] documentation: Add scheduler/sched-avg.txt

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Date:	Mon, 16 May 2016 02:59:27 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	bsegall@...gle.com, pjt@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	juri.lelli@....com, Yuyang Du <yuyang.du@...el.com>
Subject: [RFC PATCH 2/9] documentation: Add scheduler/sched-avg.txt

This doc file has the program to generate the constants to compute
sched averages.

Signed-off-by: Yuyang Du <yuyang.du@...el.com>
---
 Documentation/scheduler/sched-avg.txt |   94 +++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Documentation/scheduler/sched-avg.txt

diff --git a/Documentation/scheduler/sched-avg.txt b/Documentation/scheduler/sched-avg.txt
new file mode 100644
index 0000000..45be4bd
--- /dev/null
+++ b/Documentation/scheduler/sched-avg.txt
@@ -0,0 +1,94 @@
+The following program is used to generate the constants for
+computing sched averages.
+
+==============================================================
+		C program (compile with -lm)
+==============================================================
+
+#include <math.h>
+#include <stdio.h>
+
+#define HALFLIFE 32
+#define SHIFT 32
+
+double y;
+
+void calc_decay_inv_multiply() {
+	int i;
+	unsigned int x;
+
+	printf("static const u32 __decay_inv_multiply_N[] = {");
+	for(i = 0; i < HALFLIFE; i++) {
+		x = ((1UL<<32)-1)*pow(y, i);
+
+		if (i % 6 == 0) printf("\n\t");
+		printf("0x%8x, ", x);
+	}
+	printf("\n};\n\n");
+}
+
+int sum = 1024;
+void calc_accumulated_sum() {
+	int i;
+
+	printf("static const u32 __accumulated_sum_N[] = {\n\t    0,");
+	for(i = 1; i <= HALFLIFE; i++) {
+		if (i == 1)
+			sum *= y;
+		else
+			sum = sum*y + 1024*y;
+
+		if (i % 11 == 0) printf("\n\t");
+		printf("%5d,", sum);
+	}
+	printf("\n};\n\n");
+}
+
+int n = 1;
+/* first period */
+long max = 1024;
+
+void calc_converged_max() {
+	long last = 0, y_inv = ((1UL<<32)-1)*y;
+
+	for (; ; n++) {
+		if (n > 1)
+			max = ((max*y_inv)>>SHIFT) + 1024;
+			/*
+			 * This is the same as:
+			 * max = max*y + 1024;
+			 */
+
+		if (last == max)
+			break;
+
+		last = max;
+	}
+	n--;
+	printf("#define SCHED_AVG_HALFLIFE %d\n", HALFLIFE);
+	printf("#define SCHED_AVG_MAX %ld\n", max);
+	printf("#define SCHED_AVG_MAX_N %d\n\n", n);
+}
+
+void calc_accumulated_sum_32() {
+	int i, x = sum;
+
+	printf("static const u32 __accumulated_sum_N32[] = {\n\t     0,");
+	for(i = 1; i <= n/HALFLIFE+1; i++) {
+		if (i > 1)
+			x = x/2 + sum;
+
+		if (i % 6 == 0) printf("\n\t");
+		printf("%6d,", x);
+	}
+	printf("\n};\n\n");
+}
+
+void main() {
+	y = pow(0.5, 1/(double)HALFLIFE);
+
+	calc_decay_inv_multiply();
+	calc_accumulated_sum();
+	calc_converged_max();
+	calc_accumulated_sum_32();
+}
-- 
1.7.9.5