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  • Yorick Peterse's avatar
    Use clock_gettime for all performance timestamps · 1dcacfe1c34b
    Yorick Peterse authored
    Process.clock_gettime allows getting the real time in nanoseconds as
    well as allowing one to get a monotonic timestamp. This offers greater
    accuracy without the overhead of having to allocate a Time instance. In
    general using Time.now/Time.new is about 2x slower than using
    Process.clock_gettime(). For example:
    
        require 'benchmark/ips'
    
        Benchmark.ips do |bench|
          bench.report 'Time.now' do
            Time.now.to_f
          end
    
          bench.report 'clock_gettime' do
            Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
          end
    
          bench.compare!
        end
    
    Running this benchmark gives:
    
        Calculating -------------------------------------
                    Time.now   108.052k i/100ms
               clock_gettime   125.984k i/100ms
        -------------------------------------------------
                    Time.now      2.343M (± 7.1%) i/s -     11.670M
               clock_gettime      4.979M (± 0.8%) i/s -     24.945M
    
        Comparison:
               clock_gettime:  4979393.8 i/s
                    Time.now:  2342986.8 i/s - 2.13x slower
    
    Another benefit of using Process.clock_gettime() is that we can simplify
    the code a bit since it can give timestamps in nanoseconds out of the
    box.
    1dcacfe1c34b