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Subject: Re: zsh slow and hogs cpu when using */*/*.ext on large file tree
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From: Piotr Karbowski <jabberuser@gmail.com>
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Date: Sat, 12 Dec 2015 17:43:18 +0100
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Hi,

On 12/12/2015 05:33 PM, Sebastian Gniazdowski wrote:
 > PS. I wonder if operating system didn't cache the work that zsh has
 > done. In other words, in such situation, every following run of */*/*
 > will be fast. That's why I couldn't test this on my machine (which is
 > OS X) and I asked you to test.
 >
 > If you are somehow able to overcome operating system optimizations
 > (i.e. e.g. every run of */*/* on 5.1.1 is 20 seconds long) then the
 > values you gave are reliable and usable. Otherwise, bash my benefit
 > from zsh run.

Actually it does not seems that 5.1.1 is much slower than 5.2. My report 
was wrong as the grep did not showed up for 20s as with first X files it 
wasn't finding anyting, here I've tested with ls.

But anyways, if I drop the VFS caches with `echo 3 > 
/proc/sys/vm/drop_caches` before every test, the zsh 5.2 takes 5.546s 
and bash 4.3.42 takes 3.295 thus we can presume that the VFS layer on 
ext4 filesystem I run here takes about 3.0s, rest is within the userspace.

-- Piotr.