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

> 
> On Tue, Jul 13 2021, Jeff Hostetler wrote:
> 
>> On 7/1/21 7:09 PM, Ævar Arnfjörð Bjarmason wrote:
>>> On Thu, Jul 01 2021, Jeff Hostetler via GitGitGadget wrote:
>>>
>>>> From: Jeff Hostetler <jeffhost@microsoft.com>
>>>>
>>>> Change p7519 to use a single "test-tool touch" command to update
>>>> the mtime on a series of (thousands) files instead of invoking
>>>> thousands of commands to update a single file.
>>>>
>>>> This is primarily for Windows where process creation is so
>>>> very slow and reduces the test run time by minutes.
>>>>
>>>> Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
>>>> ---
>>>>    t/perf/p7519-fsmonitor.sh | 14 ++++++--------
>>>>    1 file changed, 6 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/t/perf/p7519-fsmonitor.sh b/t/perf/p7519-fsmonitor.sh
>>>> index 5eb5044a103..f74e6014a0a 100755
>>>> --- a/t/perf/p7519-fsmonitor.sh
>>>> +++ b/t/perf/p7519-fsmonitor.sh
>>>> @@ -119,10 +119,11 @@ test_expect_success "one time repo setup" '
>>>>    	fi &&
>>>>      	mkdir 1_file 10_files 100_files 1000_files 10000_files &&
>>>> -	for i in $(test_seq 1 10); do touch 10_files/$i; done &&
>>>> -	for i in $(test_seq 1 100); do touch 100_files/$i; done &&
>>>> -	for i in $(test_seq 1 1000); do touch 1000_files/$i; done &&
>>>> -	for i in $(test_seq 1 10000); do touch 10000_files/$i; done &&
>>>> +	test-tool touch sequence --pattern="10_files/%d" --start=1 --count=10 &&
>>>> +	test-tool touch sequence --pattern="100_files/%d" --start=1 --count=100 &&
>>>> +	test-tool touch sequence --pattern="1000_files/%d" --start=1 --count=1000 &&
>>>> +	test-tool touch sequence --pattern="10000_files/%d" --start=1 --count=10000 &&
>>>> +
>>>>    	git add 1_file 10_files 100_files 1000_files 10000_files &&
>>>>    	git commit -qm "Add files" &&
>>>>    @@ -200,15 +201,12 @@ test_fsmonitor_suite() {
>>>>    	# Update the mtimes on upto 100k files to make status think
>>>>    	# that they are dirty.  For simplicity, omit any files with
>>>>    	# LFs (i.e. anything that ls-files thinks it needs to dquote).
>>>> -	# Then fully backslash-quote the paths to capture any
>>>> -	# whitespace so that they pass thru xargs properly.
>>>>    	#
>>>>    	test_perf_w_drop_caches "status (dirty) ($DESC)" '
>>>>    		git ls-files | \
>>>>    			head -100000 | \
>>>>    			grep -v \" | \
>>>> -			sed '\''s/\(.\)/\\\1/g'\'' | \
>>>> -			xargs test-tool chmtime -300 &&
>>>> +			test-tool touch stdin &&
>>>>    		git status
>>>>    	'
>>> 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.
> 
> There's what Elijah mentioned about test_seq, so maybe it's just that.
> 
> But what I was suggesting was using the xargs mode where it does N
> arguments at a time.
> 
> Does this work for you, and does it cause xargs to invoke "touch" with
> the relevant N number of arguments, and does it help with the
> performance?
> 
>      test_seq 1 10000 | xargs touch
>      test_seq 1 10000 | xargs -n 10 touch
>      test_seq 1 10000 | xargs -n 100 touch
>      test_seq 1 10000 | xargs -n 1000 touch

> 
> etc.
> 
> Also I didn't notice this before, but the -300 part of "chmtime -300"
> was redundant before then? I.e. you're implicitly changing it to "=+0"
> instead with your "touch" helper, are you not?
>