Re: [PATCH v3 24/34] t/perf/p7519: speed up test using "test-tool touch"

[Jeff Hostetler <git@jeffhostetler.com>]

On 7/13/21 1:36 PM, Elijah Newren wrote:
> On Tue, Jul 13, 2021 at 10:10 AM Jeff Hostetler <git@jeffhostetler.com> wrote:
>>
>> On 7/1/21 7:09 PM, Ævar Arnfjörð Bjarmason wrote:
>>>
>>> Did you try to replace this with some variant of:
>>>
>>>       test_seq 1 10000 | xargs touch
>>>
>>> Which (depending on your xargs version) would invoke "touch" commands
>>> with however many argv items it thinks you can handle.
>>
>> a quick test on my Windows machine shows that
>>
>>          test_seq 1 10000 | xargs touch
>>
>> takes 3.1 seconds.
>>
>> just a simple
>>
>>          test_seq 1 10000 >/dev/null
>>
>> take 0.2 seconds.
>>
>> using my test-tool helper cuts that time in half.
> 
> Yeah, test_seq is pretty bad; it's just a loop in shell.  Is there a
> 'seq' on windows, and does using it instead of test_seq make things
> faster with Ævar's suggested command?
> 

The Git for Windows SDK bash environment does have a /usr/bin/seq
which appears to be from GNU coreutils 8.32.  (This is different
from the version that I have on my Mac (which doesn't have a version
number).)

Using it:

	seq 1 10000 >/dev/null

takes 0.04 seconds instead of 0.2.

However, it doesn't help the touch.

	seq 1 10000 | xargs touch

still takes ~3.1 seconds.

FWIW, the xargs is clustering the 10,000 files into ~4 command lines,
so there is a little bit of Windows process overhead, but not that
much.

	seq 1 10000 | xargs wc -l | grep total

> I'd really like to modify test_seq to use seq when it's available and
> fall back to the looping-in-shell when we need to for various
> platforms.
> 
> Maybe it'd even make sense to write a 'test-tool seq' and make
> test_seq use that just so we can rip out that super lame shell
> looping.
>