From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: "SZEDER Gábor" <szeder.dev@gmail.com>
Cc: Johannes Sixt <j6t@kdbg.org>, git@vger.kernel.org
Subject: Re: [PATCH 1/3] t7610-mergetool: do not place pipelines headed by `yes` in subshells
Date: Mon, 10 Jun 2019 20:29:56 +0200 (CEST) [thread overview]
Message-ID: <nycvar.QRO.7.76.6.1906102026030.789@QRFXGBC-DHN364S.ybpnyqbznva> (raw)
In-Reply-To: <20190610095942.GA19035@szeder.dev>
[-- Attachment #1: Type: text/plain, Size: 2147 bytes --]
Hi,
On Mon, 10 Jun 2019, SZEDER Gábor wrote:
> > diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
> > index 5b61c10a9c..b67440882b 100755
> > --- a/t/t7610-mergetool.sh
> > +++ b/t/t7610-mergetool.sh
> > @@ -131,13 +131,13 @@ test_expect_success 'custom mergetool' '
> > git checkout -b test$test_count branch1 &&
> > git submodule update -N &&
> > test_must_fail git merge master &&
> > - ( yes "" | git mergetool both ) &&
> > - ( yes "" | git mergetool file1 file1 ) &&
> > - ( yes "" | git mergetool file2 "spaced name" ) &&
> > - ( yes "" | git mergetool subdir/file3 ) &&
> > - ( yes "d" | git mergetool file11 ) &&
> > - ( yes "d" | git mergetool file12 ) &&
> > - ( yes "l" | git mergetool submod ) &&
> > + yes "" | git mergetool both &&
> > + yes "" | git mergetool file1 file1 &&
> > + yes "" | git mergetool file2 "spaced name" &&
> > + yes "" | git mergetool subdir/file3 &&
> > + yes "d" | git mergetool file11 &&
> > + yes "d" | git mergetool file12 &&
> > + yes "l" | git mergetool submod &&
> > test "$(cat file1)" = "master updated" &&
> > test "$(cat file2)" = "master new" &&
> > test "$(cat subdir/file3)" = "master new sub" &&
>
> Another possibility for eliminating a few more subshells might be to
> turn these
>
> test "$(cat file1)" = "that"'
>
> checks into
>
> echo that >expect &&
> test_cmp expect file1
>
> because 'test_cmp' on Windows first compares the two files in shell
> and runs 'diff' only when there is a difference to report.
When you remember that spawning processes is much more expensive on
Windows, still, than I/O, you will realize that this adds even more
expense. Instead of a spawn & read, you are suggesting essentially a
write, spawn, read & read, and that is only the best case.
In the worst case, it would be a write, spawn, read & read, spawn, read &
read.
(Even if the first spawn is an MSYS2 spawn on Windows, which is more
expensive than the MINGW spawn for the `git diff`, if that is a `git diff`
rather than `diff`, didn't check...)
So I am rather negative about this suggestion ;-)
Ciao,
Dscho
next prev parent reply other threads:[~2019-06-10 18:29 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 8:58 [PATCH 0/3] Reduce number of processes spawned by git-mergetool Johannes Sixt
2019-06-10 8:58 ` [PATCH 1/3] t7610-mergetool: do not place pipelines headed by `yes` in subshells Johannes Sixt
2019-06-10 9:59 ` SZEDER Gábor
2019-06-10 17:23 ` Junio C Hamano
2019-06-10 17:56 ` SZEDER Gábor
2019-06-10 18:29 ` Johannes Schindelin [this message]
2019-06-10 18:57 ` SZEDER Gábor
2019-06-10 8:58 ` [PATCH 2/3] mergetool: dissect strings with shell variable magic instead of `expr` Johannes Sixt
2019-06-10 17:17 ` Junio C Hamano
2019-06-10 21:34 ` Johannes Sixt
2019-06-10 8:59 ` [PATCH 3/3] mergetool: use shell variable magic instead of `awk` Johannes Sixt
2019-06-10 17:21 ` Junio C Hamano
2019-06-10 22:01 ` Johannes Sixt
2019-06-12 16:33 ` [PATCH v2 0/4] Reduce number of processes spawned by git-mergetool Johannes Sixt
2019-06-12 16:33 ` [PATCH v2 1/4] t7610-mergetool: do not place pipelines headed by `yes` in subshells Johannes Sixt
2019-06-12 16:33 ` [PATCH v2 2/4] t7610-mergetool: use test_cmp instead of test $(cat file) = $txt Johannes Sixt
2019-06-12 16:33 ` [PATCH v2 3/4] mergetool: dissect strings with shell variable magic instead of `expr` Johannes Sixt
2019-06-12 16:33 ` [PATCH v2 4/4] mergetool: use shell variable magic instead of `awk` Johannes Sixt
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