CODEWITHSUNDEEP
rubymacos
Nathan Long
Nathan Long

Reputation: 126042

How can I diagnose my very slow Ruby startup times?

Intermittently, when I type a command that involves Ruby (like ruby somefile.rb, rake, rspec spec, or irb), it takes a long time for the command to execute. For example, a few minutes ago, it took about a minute for irb to start. A few seconds ago, it took about a second.

While waiting for irb to start, I pressed Control + T repeatedly. Some output I saw included:

load: 1.62  cmd: ruby 12374 uninterruptible 0.45u 0.13s
load: 1.62  cmd: ruby 12374 uninterruptible 0.48u 0.13s
load: 1.62  cmd: ruby 12374 uninterruptible 0.53u 0.15s

On OSX, this output represents "load, command running, pid, status, and user and system CPU time used". It appears that when I had been waiting 53 seconds, the CPU time used was only 0.15 seconds.

My understanding of load is that it's roughly "how many cores are being used". Eg, on a one-core system, 1.0 is full utilization, but on a four-core machine, it's 25% utilization. I don't think the amount of load is the problem, because my machine is multi-core. Also, when irb starts quickly, I can get one line of output with Control + T that's also above 1.0.

load: 1.22  cmd: ruby 12452 running 0.26u 0.02s

I also notice that in the good case, the status is "running", not "uninterruptible".

How can I diagnose and fix these slow startups?

Upvotes: 3

Views: 925

Answers (1)

digitalextremist
digitalextremist

Reputation: 5993

This is a longshot. Try installing haveged.

I've seen this problem before. That solved it for me. Sometimes there is not enough entropy for libraries or elements of Ruby which are trying to load up a pool of random numbers.

If you notice that the time for something to start goes quickly when you are typing more, moving your mouse, using a lot of network traffic -- then it's entropy, which would go against most of what you'd think.

If there is more processor and RAM usage, more interaction with the system, etc - you'd think it'd be slower, but in entropy depletion situations, that's actually exactly what you need.

Upvotes: 1

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