From: Eric Wong <normalperson@...>
Date: 2014-08-30T06:34:28+00:00
Subject: [ruby-core:64668] Re: [ruby-trunk - Bug #10188] [Open] Regression of Benchmark.realtime

shibata.hiroshi@gmail.com wrote:
> I investigate this on Amazon Linux 2014.3

Is this shared machine/VM?  What kernel config/version?

Kernel config may be in /proc/config.* , otherwise distros may put
kernel config in /boot/config*

I'm mainly interested in *_HZ and preempt options.

> https://gist.github.com/hsbt/2647af71d60121034c1c
> 
> In this results, ```Benchmark.realtime { sleep 0.001 }``` returns 0.01 every 10 times. 

Yikes, wild timings :<

> > Eric Wong
> 
> How about do you think this fail?

I think the test case is too fragile.  We should increase delta+sleep or
remove test.  Based on comments on thread_pthread.c, 0.1s might be a
lower bound on portable timing granularity.

I think this can fail on your system even with the lib/benchmark.rb
optimization in r47260 reverted.