Class: PSI::Sampler

Inherits:
Object
  • Object
show all
Defined in:
lib/psi/sampler.rb

Overview

Calculates exact stall ratios from cumulative PSI totals.

Instance Method Summary collapse

Constructor Details

#initialize(resource, cgroup: nil) ⇒ Sampler

Returns a new instance of Sampler.



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# File 'lib/psi/sampler.rb', line 9

def initialize(resource, cgroup: nil)
  @resource = resource
  @cgroup = cgroup
end

Instance Method Details

#sample ⇒ Delta?

Takes a sample and returns a delta after the first call.

Returns:



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# File 'lib/psi/sampler.rb', line 16

def sample
  reading = PSI.read(@resource, cgroup: @cgroup)
  sampled_at = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  return remember(reading, sampled_at) unless @previous

  elapsed = sampled_at - @sampled_at
  previous = @previous
  remember(reading, sampled_at)
  Delta.new(
    some_ratio: ratio(reading.some, previous.some, elapsed),
    full_ratio: ratio(reading.full, previous.full, elapsed),
    elapsed: elapsed
  )
end