问题描述
有人可以向我解释为什么Process.fork
使Ruby中的内容变得这么慢吗?我在OS X El Capitan上使用Ruby 2.3.1.
Can someone explain to me why Process.fork
makes stuff so much slower in Ruby? I'm using Ruby 2.3.1 on OS X El Capitan.
require 'time'
require 'benchmark'
def do_stuff
50000.times { Time.parse(Time.utc(2016).iso8601) }
end
puts Benchmark.measure { do_stuff } # => 1.660000 0.010000 1.670000 ( 1.675466)
Process.fork do
puts Benchmark.measure { do_stuff } # => 3.170000 6.250000 9.420000 ( 9.508235)
end
刚注意到,在Linux(经测试的Debian或Ubuntu)上运行该代码不会对性能产生负面影响.
Just noticed that running that code on Linux (tested Debian or Ubuntu) does not result in a negative performance impact.
推荐答案
为什么Process.fork会使OS X上的Ruby中的内容变慢?"
深入了解这一点的第一步是减少变量的数量.
Step one in getting to the bottom of this is to reduce the number of variables.
您运行5万次Time.parse(Time.utc(2016).iso8601)
的示例似乎很奇怪.我使用另一个慢速" Ruby任务重新构建了基准测试:
Your example of running Time.parse(Time.utc(2016).iso8601)
fifty thousand times seems oddly specific. I reformulated the benchmark test using a different "slow" Ruby task:
require 'benchmark'
def do_stuff
a = [nil] * 200
10.times do
a.each {|x| a.each {|y| a.each {|z| ; }}}; ()
end
end
puts "main: #{Benchmark.measure { do_stuff }}"
Process.fork do
puts "fork: #{Benchmark.measure { do_stuff }}"
end
在这里,我已经在大型数组上用无操作嵌套循环替换了Time
命令.
Here I've replaced your Time
commands with a no-op nested loop over a large array.
结果:
main: 4.020000 0.010000 4.030000 ( 4.050664)
fork: 3.940000 0.000000 3.940000 ( 3.962207)
main: 3.840000 0.010000 3.850000 ( 3.856188)
fork: 3.850000 0.000000 3.850000 ( 3.865250)
main: 3.930000 0.000000 3.930000 ( 3.937741)
fork: 3.970000 0.000000 3.970000 ( 3.986397)
main: 4.340000 0.010000 4.350000 ( 4.370009)
fork: 4.300000 0.000000 4.300000 ( 4.308156)
没有明显的分叉过程变慢或变快的现象.我已经在OS X和Ubuntu上的Ruby 1.9、2.0和2.3中进行了测试,并且保持不变.
No noticeable pattern of the forked process being slower or faster. I've tested in Ruby 1.9, 2.0, and 2.3 on both OS X and Ubuntu, and it remains the same.
您的问题的答案是:
Process.fork
不会使OS X上的Ruby的内容变慢.
Process.fork
does not, in general, make stuff slower in Ruby on OS X.
但是,这里还有一个有趣的问题,它是
However, there is a different interesting question here, which is Why is `Time.utc` slower in a forked process in Ruby on OS X (and not in Python)?
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