From: Johannes Sixt <j.sixt@viscovery.net>
Date: Tue, 09 Nov 2010 11:42:55 GMT
Subject: Re: [RFC/PATCH 1/5] gettext: fix bug in git-sh-i18n's eval_gettext() by using envsubst(1)
Message-ID: <4CD933BF.6070105@viscovery.net>
In-Reply-To: <AANLkTins_qq=unv101JuV_CVvkp3KbTq5qycva7bZ7sm@mail.gmail.com>

Am 11/9/2010 11:52, schrieb Ævar Arnfjörð Bjarmason:
> On Tue, Nov 9, 2010 at 11:36, Johannes Sixt <j.sixt@viscovery.net> wrote:
>> $ time (for i in {1..100}; do git version; done) > /dev/null
>>
>> real    0m5.610s
...
>> $ time (for i in {1..100}; do eval_gettext foobar; done) > /dev/null
>>
>> real    0m20.578s
...
>> Note that there are only 100 iterations, so we are talking about 0.2
>> seconds per eval_gettext call! That's an awful lot of time even for a
>> single error message.
> 
> Thanks for elaborating. But just so I understand you correctly it's a
> cost of invoking *any* program in shellscripts on Windows? So e.g. 10
> sed calls would cost the same as 10 git-sh-i18n--envsubst calls (but
> of course 5 eval_gettext() calls, since it calls git-sh-i18n--envsubst
> twice).

An invocation of sed, cat, etc. (POSIX/MSYS tools) is cheaper by a factor
of 2 than a git invocation for a reason that I do not understand. (Perhaps
it has to do with the number of DLLs that are linked; git has 9 static
dependencies, MSYS tools only 3.)

eval_gettext involves 2 git invocation (git-sh-i18n--envsubst counts as
much as git) and 1 subshell in practice (some subshells are optimized away).

> So e.g. using eval_gettext once isn't a bigger problem than calling
> some trivial sed substitution twice?

Look at the timings: In my book, eval_gettext counts like about 8 sed
substitutions.

-- Hannes