Created gh-images branch for storing images

metadata-cost.py

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+#!/usr/bin/env python
+
+import matplotlib
+matplotlib.use('SVG')
+import matplotlib.pyplot as plt
+import numpy as np
+
+matplotlib.rc('font', family='sans-serif', size=11)
+matplotlib.rc('axes', titlesize='medium', labelsize='medium')
+matplotlib.rc('xtick', labelsize='small')
+matplotlib.rc('ytick', labelsize='small')
+
+fig, ax = plt.subplots(figsize=(6, 3.5))
+ax.set_title('Metadata pair update cost')
+
+# multiplicative cost of metadata
+def cost(r, n, size):
+    cost = n + n*(r*(size/n) / ((1-r)*(size/n) + 1))
+    return cost / n
+
+t = np.arange(0.0, 1.0, 0.01)
+ax.plot(t, cost(t, 100, 4096))
+
+ax.set_xlabel('% full')
+ax.set_xlim(0, 1)
+ax.set_ylabel('multiplicative cost')
+ax.set_ylim(0, 12)
+
+xticks = np.arange(0.0, 1+0.1, 0.2)
+ax.set_xticks(xticks)
+ax.set_xticklabels(['%d%%' % (100*t) for t in xticks])
+yticks = np.arange(0, 12+1, 2)
+ax.set_yticks(yticks)
+ax.set_yticklabels(['%dx' % t for t in yticks])
+
+ax.spines['right'].set_visible(False)
+ax.spines['top'].set_visible(False)
+
+fig.tight_layout()
+plt.savefig('metadata-cost.svg', bbox_inches="tight")