pull-cpu-throttle

A pull-stream "through stream" that does CPU throttling to avoid overheating the CPU

npm install --save pull-cpu-throttle

Usage

Default use

const pull = require('pull-stream');
const cpuThrottle = require('pull-cpu-throttle');

pull(
  pull.count(1000000),
  cpuThrottle(),
  pull.drain(x => console.log(x)),
);

Tweaking the parameters

This module pulls from the source, but once in a while it will check the CPU usage, and if it has gone above the limit known as the ceiling, it pauses for wait milliseconds, and then resumes, in such a way that it should stay close to the limit. In other words, two parameters control the pulling:

• ceiling: the maximum CPU usage you want the task to consume, approximately, in percentages (100 is 100%, not 1)
• wait: the waiting period, in milliseconds, to pause in order to allow other tasks to use the CPU

The default CPU ceiling is 88% and the default waiting period for each pause is 144ms (roughly 9 frames if you have the UI running at 60fps). This means that the longest pause during which no pull will occur is 144ms.

To configure your own parameters, pass an opts object as the argument:

const pull = require('pull-stream');
const cpuThrottle = require('pull-cpu-throttle');

pull(
  pull.count(1000000),
  cpuThrottle({ceiling: 90, wait: 90}),
  pull.drain(x => console.log(x)),
);

To configure these parameters, consider that:

• The greater the ceiling is, the closer the stream will behaves as if you were had no cpuThrottle(), i.e. the less gently it pulls the source with regards to CPU load
• The smaller the ceiling is, the more time it will take to consume the source, i.e. the slower your application will run overall
• The greater the wait, the more the actual CPU usage fluctuates below and above the ceiling, i.e. the more bumpy the ride is for CPU usage and workload throughput
• The smaller the wait, the more the actual CPU usage accurately meets the ceiling, but also the more overhead there is with many short-lived timers for those pauses

The total time for drainage is also important. Having no cpuThrottle() is the fastest, with the shortest total time. Adding cpuThrottle() with a small wait might give a total drainage time of approx. 2.5x that of pull.drain. The defaults ceiling=88, wait=144 are a sweet spot, and it can achieve a total drainage time of approx 1.4x that of pure pull.drain without CPU throttling. You can run benchmarks yourself by running cd perf && ./run-all.sh in this repository.

The chart below shows results for running the benchmark in perf on Ubuntu 18.04.3 x86_64, Intel® Core™ i7-7500U CPU @ 2.70GHz × 4, 15,4 GiB RAM, for different values of ceiling (c) and wait (w).

License

MIT