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import numpy
import random
from matplotlib import pyplot
percentiles = [50, 75, 90, 95, 99]
latencies = [[] for p in percentiles]
loads = []
n = 100000
for k in numpy.linspace(0.01, 1.0, 100):
print('k =', k)
query_enqueued = numpy.cumsum(numpy.random.exponential(size=(n,), scale=1./k))
query_time = numpy.random.lognormal(size=(n,))
query_finished = numpy.zeros((n, ))
for i in range(n):
query_finished[i] = query_enqueued[i] + query_time[i]
if i > 0:
# Can't finish before the previous query finished plus the time for this query
query_finished[i] = max(query_finished[i], query_finished[i-1] + query_time[i])
for p, l in zip(percentiles, latencies):
l.append(numpy.percentile(query_finished - query_enqueued, p))
loads.append(numpy.sum(query_time) / numpy.max(query_enqueued))
for p, l in zip(percentiles, latencies):
pyplot.semilogy(loads, l, label='%d%% percentile latency' % p)
pyplot.xlim([0, 1])
pyplot.ylim([0, 20])
pyplot.legend(loc='lower right')

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@erikbern erikbern commented Feb 12, 2018



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