t/perf/run: fix bin-wrappers computation

[derrickstolee]

Found this while we were testing sparse index improvements to 'git stash', which uses a lot of subcommands.

Thanks,
-Stolee

cc: gitster@pobox.com
cc: avarab@gmail.com
cc: vdye@github.com
cc: stolee@gmail.com
cc: Taylor Blau me@ttaylorr.com

[derrickstolee]

/submit

[gitgitgadget]

Submitted as pull.1044.git.1632239172735.gitgitgadget@gmail.com

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git pr-1044/derrickstolee/perf-run-v1

To fetch this version to local tag pr-1044/derrickstolee/perf-run-v1:

git fetch --no-tags https://github.com/gitgitgadget/git tag pr-1044/derrickstolee/perf-run-v1

[gitgitgadget]

On the Git mailing list, Taylor Blau wrote (reply to this):

On Tue, Sep 21, 2021 at 03:46:12PM +0000, Derrick Stolee via GitGitGadget wrote:
> This is critical to successfully computing performance of commands that
> execute subcommands. The bin-wrappers ensure that the --exec-path is set
> correctly.

Just sanity-checking everything you said: with this bug, we'll set
mydir_abs_wrappers to "/bin-wrappers", then realize that directory
doesn't exist, and fall back to GIT_TEST_INSTALLED=$mydir_abs. Putting
'set -x' at the top of t/perf/run, we can see the relevant section:

  + mydir=build/73cd7d9420bb7d75207e8149521db375c789a81c
  + cd build/73cd7d9420bb7d75207e8149521db375c789a81c
  + pwd
  + mydir_abs=/home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
  + mydir_abs_wrappers=/bin-wrappers
  + test -d /bin-wrappers
  + GIT_TEST_INSTALLED=/home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
  + export GIT_TEST_INSTALLED

OK. But the real problem is in t/test-lib.sh where we read
"$GIT_TEST_INSTALLED". There we ask for the `--exec-path`, which appears
to be wrong, at least in my setup. Printing out the $GIT_EXEC_PATH and
$GIT_TEST_INSTALLED, I get:

  /home/ttaylorr/local/git/ds.sparse-checkout/libexec/git-core,
  /home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c

where the former is the branch I happen to have checked out, and the
latter is the revision that I asked to run performance tests on via
t/perf/run.

So I think we'll run the right top-level Git command since the latter
path ends up first in our $PATH, but the exec path is definitely wrong.

> diff --git a/t/perf/run b/t/perf/run
> index d19dec258a2..55219aa4056 100755
> --- a/t/perf/run
> +++ b/t/perf/run
> @@ -74,7 +74,7 @@ set_git_test_installed () {
>  	mydir=$1
>
>  	mydir_abs=$(cd $mydir && pwd)
> -	mydir_abs_wrappers="$mydir_abs_wrappers/bin-wrappers"
> +	mydir_abs_wrappers="$mydir_abs/bin-wrappers"

This fix looks obviously right to me (and gives me the expected output
from above when I apply it locally).

Thanks,
Taylor

[gitgitgadget]

User Taylor Blau <me@ttaylorr.com> has been added to the cc: list.

[gitgitgadget]

On the Git mailing list, Derrick Stolee wrote (reply to this):

On 9/21/2021 1:50 PM, Taylor Blau wrote:
> On Tue, Sep 21, 2021 at 03:46:12PM +0000, Derrick Stolee via GitGitGadget wrote:
>> This is critical to successfully computing performance of commands that
>> execute subcommands. The bin-wrappers ensure that the --exec-path is set
>> correctly.
> 
> Just sanity-checking everything you said: with this bug, we'll set
> mydir_abs_wrappers to "/bin-wrappers", then realize that directory
> doesn't exist, and fall back to GIT_TEST_INSTALLED=$mydir_abs. Putting
> 'set -x' at the top of t/perf/run, we can see the relevant section:
> 
>   + mydir=build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + cd build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + pwd
>   + mydir_abs=/home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + mydir_abs_wrappers=/bin-wrappers
>   + test -d /bin-wrappers
>   + GIT_TEST_INSTALLED=/home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + export GIT_TEST_INSTALLED
> 
> OK. But the real problem is in t/test-lib.sh where we read
> "$GIT_TEST_INSTALLED". There we ask for the `--exec-path`, which appears
> to be wrong, at least in my setup. Printing out the $GIT_EXEC_PATH and
> $GIT_TEST_INSTALLED, I get:
> 
>   /home/ttaylorr/local/git/ds.sparse-checkout/libexec/git-core,
>   /home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
> 
> where the former is the branch I happen to have checked out, and the
> latter is the revision that I asked to run performance tests on via
> t/perf/run.
> 
> So I think we'll run the right top-level Git command since the latter
> path ends up first in our $PATH, but the exec path is definitely wrong.

Thanks for digging into this more. This issue with GIT_EXEC_PATH explains
some strangeness I was seeing.

Perhaps there is something more robust to be done around GIT_EXEC_PATH,
but the current fix satisfies my needs.
 
>> diff --git a/t/perf/run b/t/perf/run
>> index d19dec258a2..55219aa4056 100755
>> --- a/t/perf/run
>> +++ b/t/perf/run
>> @@ -74,7 +74,7 @@ set_git_test_installed () {
>>  	mydir=$1
>>
>>  	mydir_abs=$(cd $mydir && pwd)
>> -	mydir_abs_wrappers="$mydir_abs_wrappers/bin-wrappers"
>> +	mydir_abs_wrappers="$mydir_abs/bin-wrappers"
> 
> This fix looks obviously right to me (and gives me the expected output
> from above when I apply it locally).

Thanks,
-Stolee

[gitgitgadget]

This branch is now known as ds/perf-test-built-path-fix.

[gitgitgadget]

This patch series was integrated into seen via git@132d623.

[gitgitgadget]

This patch series was integrated into seen via git@947f0ee.

[gitgitgadget]

This patch series was integrated into seen via git@886f9da.

[gitgitgadget]

This patch series was integrated into seen via git@d06889b.

[gitgitgadget]

There was a status update in the "New Topics" section about the branch ds/perf-test-built-path-fix on the Git mailing list:

Perf test fix.

Will merge to 'next'.

[gitgitgadget]

There was a status update in the "Cooking" section about the branch ds/perf-test-built-path-fix on the Git mailing list:

Perf test fix.

Will merge to 'next'.

[gitgitgadget]

This patch series was integrated into seen via git@1a35c2f.

[gitgitgadget]

This patch series was integrated into next via git@18a2148.