sched/Documentation: Add 'sched-pelt' tool

Add a user-space program to compute/generate the PELT constants.

The kernel/sched/sched-pelt.h header will contain the output of
this program.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: matt@codeblueprint.co.uk
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1486935863-25251-2-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/Documentation/scheduler/sched-pelt.c b/Documentation/scheduler/sched-pelt.c
new file mode 100644 (file)
index 0000000..e421913
--- /dev/null
+++ b/Documentation/scheduler/sched-pelt.c
@@ -0,0 +1,108 @@
+/*
+ * 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_runnable_avg_yN_inv(void)
+{
+       int i;
+       unsigned int x;
+
+       printf("static const u32 runnable_avg_yN_inv[] = {");
+       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_runnable_avg_yN_sum(void)
+{
+       int i;
+
+       printf("static const u32 runnable_avg_yN_sum[] = {\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(void)
+{
+       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 LOAD_AVG_PERIOD %d\n", HALFLIFE);
+       printf("#define LOAD_AVG_MAX %ld\n", max);
+//     printf("#define LOAD_AVG_MAX_N %d\n\n", n);
+}
+
+void calc_accumulated_sum_32(void)
+{
+       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(void)
+{
+       printf("/* Generated by Documentation/scheduler/sched-pelt; do not modify. */\n\n");
+
+       y = pow(0.5, 1/(double)HALFLIFE);
+
+       calc_runnable_avg_yN_inv();
+//     calc_runnable_avg_yN_sum();
+       calc_converged_max();
+//     calc_accumulated_sum_32();
+}