[PATCH 14/50] mars: add new file drivers/block/mars/lib_rank.c

[Thomas Schoebel-Theuer]

Signed-off-by: Thomas Schoebel-Theuer <tst@xxxxxxxxxxxxxxxxxx>
---
 drivers/block/mars/lib_rank.c | 73 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 drivers/block/mars/lib_rank.c

diff --git a/drivers/block/mars/lib_rank.c b/drivers/block/mars/lib_rank.c
new file mode 100644
index 0000000..384cb61
--- /dev/null
+++ b/drivers/block/mars/lib_rank.c
@@ -0,0 +1,73 @@
+/*  (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG */
+/*  (c) 2012 Thomas Schoebel-Theuer */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <linux/brick/lib_rank.h>
+
+void ranking_compute(struct rank_data *rkd, const struct rank_info rki[], int x)
+{
+	int points = 0;
+	int i;
+
+	for (i = 0; ; i++) {
+		int x0;
+		int x1;
+		int y0;
+		int y1;
+
+		x0 = rki[i].rki_x;
+		if (x < x0)
+			break;
+
+		x1 = rki[i+1].rki_x;
+
+		if (unlikely(x1 == RKI_DUMMY)) {
+			points = rki[i].rki_y;
+			break;
+		}
+
+		if (x > x1)
+			continue;
+
+		y0 = rki[i].rki_y;
+		y1 = rki[i+1].rki_y;
+
+		/*  linear interpolation */
+		points = ((long long)(x - x0) * (long long)(y1 - y0)) / (x1 - x0) + y0;
+		break;
+	}
+	rkd->rkd_tmp += points;
+}
+EXPORT_SYMBOL_GPL(ranking_compute);
+
+int ranking_select(struct rank_data rkd[], int rkd_count)
+{
+	int res = -1;
+	long long max = LLONG_MIN / 2;
+	int i;
+
+	for (i = 0; i < rkd_count; i++) {
+		struct rank_data *tmp = &rkd[i];
+		long long rest = tmp->rkd_current_points;
+
+		if (rest <= 0)
+			continue;
+		/* rest -= tmp->rkd_got; */
+		if (rest > max) {
+			max = rest;
+			res = i;
+		}
+	}
+	/* Prevent underflow in the long term
+	 * and reset the "clocks" after each round of
+	 * weighted round-robin selection.
+	 */
+	if (max < 0 && res >= 0) {
+		for (i = 0; i < rkd_count; i++)
+			rkd[i].rkd_got += max;
+	}
+	return res;
+}
+EXPORT_SYMBOL_GPL(ranking_select);
-- 
2.0.0

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