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Subject[PATCH v1 02/10] documentation: Add scheduler/sched-avg.txt
Date
This doc file has the program to generate the constants to compute
sched averages.

Signed-off-by: Yuyang Du <yuyang.du@intel.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
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