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Update the resource-utilization calc: average over the last N ms #127

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Oct 30, 2023
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Update the resource-utilization calc: average over the last N ms #127

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1058363
Update the resource-utilization calc to an average over the last N mi…
jfinken Oct 17, 2023
9ef7240
Update m_t1_real start
jfinken Oct 18, 2023
84e4d27
PR build_and_test fixes
jfinken Oct 23, 2023
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7 changes: 5 additions & 2 deletions performance_metrics/src/resource_usage_logger.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -49,15 +49,18 @@ void ResourceUsageLogger::start(std::chrono::milliseconds period)
std::cout << "[ResourceUsageLogger]: Logging to " << m_filename << std::endl;

m_t1_real_start = std::chrono::steady_clock::now();
m_t1_user = std::clock();
m_t1_real = std::chrono::steady_clock::now();
m_logger_thread_done = false;

// create a detached thread that monitors resource usage periodically
m_logger_thread = std::thread(
[ = ]() {
int64_t i = 1;
while (m_is_logging) {
// Updating m_t1_user and m_t1_real here will have the effect of calculating
// resource utilization only over the last `period` milliseconds, *not*
// since program start.
m_t1_user = std::clock();
m_t1_real = std::chrono::steady_clock::now();
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@jfinken jfinken Oct 18, 2023 •
edited
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@mauropasse

Ok note here how both of these members are updated right before sleep_until. Now the denominator, time_elapsed_real_ms, should reflect the period duration here.

Note that I don't think you can compare the actual value from top to what you see in the resources.txt file. As I understand it, top expresses %CPU as a percentage of total CPU time. However, here we are expressing our cpu% as the approximate CPU time used by our process over monotonic wall-clock time. e.g.

// cpu time of our process   /  monotonic wall clock time, using these
std::clock()                 / std::chrono::steady_clock::now();

I think top and our calculation are somewhat different, but I could certainly be wrong.

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@mauropasse mauropasse Oct 19, 2023 •
edited
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Yes you're right, top and our calculation are a bit different. If you multiply the CPU% we get in our way, by the number of cores of your system, the values are quite similar.
I mostly refered to the top approach of averaging every 1 or 2 seconds, so it doesn't reflect the past before that.
For that, the CPU load is what helps. I don't think we care about that so our approach is fine!

std::this_thread::sleep_until(m_t1_real_start + period * i);
if (i == 1) {
_print_header(m_file);
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2 changes: 1 addition & 1 deletion performance_test_factory/src/cli_options.cpp
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Expand Up @@ -29,7 +29,7 @@ Options::Options()
name_threads = true;
duration_sec = 5;
csv_out = false;
resources_sampling_per_ms = 500;
resources_sampling_per_ms = 1000;
tracking_options.is_enabled = false;
tracking_options.late_percentage = 20;
tracking_options.late_absolute_us = 5000;
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