> Want to give this patch a try on your collection of machines?
Not until I fix it to
+#if ADD_INTERRUPT_BENCH
+static unsigned long avg_cycles;
+
+#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
+#define FIXED_1_2 (1 << (AVG_SHIFT-1))
+
+static void add_interrupt_bench(cycles_t start)
+{
+ cycles_t duration = random_get_entropy() - start;
+
+ /* Use a weighted moving average */
+ avg_cycles += ((avg_cycles + FIXED_1_2) >> AVG_SHIFT) - duration;
+}
+#else
+#define add_interrupt_bench(x)
+#endif
+
... because the way you did it was just silly.
See net/ipv4/tcp_input.c:tcp_rtt_estimator().
That also shows you how to add a mean deviation estimator, too.
I'll go do that now...
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