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Response Time#

In context of CARET, response time is defined how much of time costs from a message input to message output of a target path. Please refer to FAQ if you are interested in response time defined in CARET.


"Response time" is generally used for the input/output of a system. Therefore, when analyzing a part of a system (when a target path is a part of end-to-end path), it should be referred to as "path latency (sum of node latency and communication latency)" rather than "response time". However, both will be referred to as "response time" for simplicity in this document.

Three cases of response time is defined; best-to-worst, best, and worst. With best case, CARET samples shortest time elapsed in a targeted path. With worst case, the previous message input timing is taken into account. best-to-worst case includes most of all cases between best and worst.

This section shows two methods to visualize response time, Histogram and Stacked Bar. Execute the following script code to load trace data and an architecture object before calling this method.

from caret_analyze.plot import Plot
from caret_analyze import Application, Architecture, Lttng
from bokeh.plotting import output_notebook, figure, show

arch = Architecture('yaml', '/path/to/architecture_file')
lttng = Lttng('/path/to/trace_data')
app = Application(arch, lttng)
path = app.get_path('target_path')


The following scripts generate histograms of response time. Horizontal axis of the histograms means response time, labeled Response Time [ms] and vertical axis of the histograms means Probability.

# plot best-to-worst case
plot = Plot.create_response_time_histogram_plot(path)


The output_notebook() is needed to show figures inside Jupyter Notebook.


# plot best case
plot = Plot.create_response_time_histogram_plot(path, case='best')


# plot worst case
plot = Plot.create_response_time_histogram_plot(path, case='worst')


Stacked Bar#

The following scripts generate stacked bar graphs of response time. Horizontal axis of the stacked bar graph means timeseries and vertical axis means Response time in the worst case or in the best case.

# plot worst case
plot = Plot.create_response_time_stacked_bar_plot(path)
# or
# plot = Plot.create_response_time_stacked_bar_plot(path, case='worst')


# plot best case
plot = Plot.create_response_time_stacked_bar_plot(path, case='best')


The horizontal axis can be changed to system time or index by changing to'index').

[worst - best] response time in legends refers to the difference in response time between the worst case and the best case.