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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Duy Nguyen <pclouds@gmail.com>
Cc: "Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
	"Git Mailing List" <git@vger.kernel.org>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Vasco Almeida" <vascomalmeida@sapo.pt>,
	"Jiang Xin" <worldhello.net@gmail.com>
Subject: Re: [PATCH] Poison gettext with the Ook language
Date: Tue, 23 Oct 2018 18:45:34 +0200
Message-ID: <871s8gd32p.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <CACsJy8CX78EbANbv8a354djJaO6dKRpXshHhHJTspJvOSewgpA@mail.gmail.com>


On Tue, Oct 23 2018, Duy Nguyen wrote:

> On Tue, Oct 23, 2018 at 12:17 PM Ævar Arnfjörð Bjarmason
> <avarab@gmail.com> wrote:
>>
>>
>> On Tue, Oct 23 2018, Johannes Schindelin wrote:
>>
>> > Hi Ævar,
>> >
>> > On Mon, 22 Oct 2018, Ævar Arnfjörð Bjarmason wrote:
>> >
>> >> So I think the only reason to keep it [GETTEXT_POISON] compile-time is
>> >> performance, but I don't think that matters. It's not like we're
>> >> printing gigabytes of _() formatted output. Everything where formatting
>> >> matters is plumbing which doesn't use this API. These messages are
>> >> always for human consumption.
>> >
>> > Well, let's make sure that your impression is correct before going too
>> > far. I, too, had the impression that gettext cannot possibly be expensive,
>> > especifally in Git for Windows' settings, where we do not even ship
>> > translations. Yet see the commit message of cc5e1bf99247 (gettext: avoid
>> > initialization if the locale dir is not present, 2018-04-21):
>> >
>> >       The runtime of a simple `git.exe version` call on Windows is
>> >       currently dominated by the gettext setup, adding a whopping ~150ms
>> >       to the ~210ms total.
>> >
>> > I would be in favor of your change to make this a runtime option, of
>> > course, as long as it does not affect performance greatly (in particular
>> > on Windows, where we fight an uphill battle to make Git faster).
>>
>> How expensive gettext() may or may not be isn't relevant to the
>> GETTEXT_POISON compile-time option.
>
> If a user requests NO_GETTEXT, they should have zero (or near zero)
> cost related to gettext. Which is true until now (the inline _()
> version is expanded to pretty much no-op with the exception of NULL
> string)

I'm assuming by "until now" you mean until my RFC patch in
https://public-inbox.org/git/875zxtd59e.fsf@evledraar.gmail.com/

Yeah it's more expensive, but I don't see how it matters. We'd be
nano-optimizing a thing that's never going to become a
bottleneck. I.e. the patch is basically taking the commented-out
codepath in this test program:

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    int have_flag(void)
    {
        return 0;
        /*
        static int flag = -1;
        if (flag == -1)
            flag = strlen(getenv("GIT_TEST_FOO"));
        return flag;
        */
    }


    int main(void)
    {
        while (1) {
            const char *out = have_flag() ? "foo" : "bar";
            puts(out);
        }
    }

When I test that on my laptop with gcc 8.2.0 I get ~230MB/s of output on
both versions, i.e. where have_flag() can be trivially constant folded,
and where we need to call getenv() for both of:

    GIT_TEST_FOO= ./main | pv >/dev/null
    GIT_TEST_FOO=1 ./main | pv >/dev/null

We don't have any codepaths where we're calling gettext() to output more
than a screenfull or two of output, so optimizing this doesn't make
sense.

>> The effect of what I'm suggesting here, and which my WIP patch in
>> <875zxtd59e.fsf@evledraar.gmail.com> implements is that we'd do a
>> one-time getenv() for each process that prints a _() message that we
>> aren't doing now, and for each message call a function that would check
>> a boolean "are we in poison mode" static global variable.
>
> Just don't do the getenv() inside _() even if you just do it one time.
> getenv() may invalidate whatever value from the previous call. I would
> not want to find out my code broke because of an getenv() inside some
> innocent _()...

How would any code break? We have various getenv("GIT_TEST_*...")
already that work the same way. Unless you set that in the environment
the function is idempotent, and I don't see how anyone would do that
accidentally.

> And we should still respect NO_GETTEXT, not doing any extra work when
> it's defined.

This is not how any of our NO_* defines work. *Sometimes* defining them
guarantees you do no extra work, but in other cases we've decided that
bending over backwards with #ifdef in various places isn't worth it.

E.g. grep_opt in grep.h is a good example of this. Even if you don't
compile with PCRE you're pointlessly memzero-ing out members of the
struct that'll never be used in your config, because it's easier to
maintain the code that way (types always checked at compile-time).

(And no, despite my involvement in PCRE I didn't introduce that
particular pattern)

For the reasons noted above I think NO_GETTEXT is another such
case. Just like GIT_TEST_SPLIT_INDEX (added in your d6e3c181bc
("read-cache: force split index mode with GIT_TEST_SPLIT_INDEX",
2014-06-13)) etc.

  reply index

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-22 15:36 Nguyễn Thái Ngọc Duy
2018-10-22 20:22 ` SZEDER Gábor
2018-10-22 20:22   ` [PATCH 1/8] test-lib.sh: preserve GIT_GETTEXT_POISON from the environment SZEDER Gábor
2018-10-22 20:22   ` [PATCH 2/8] gettext: don't poison if GIT_GETTEXT_POISON is set but empty SZEDER Gábor
2018-10-22 20:38     ` Ævar Arnfjörð Bjarmason
2018-10-22 20:22   ` [PATCH 3/8] lib-rebase: loosen GETTEXT_POISON check in fake editor SZEDER Gábor
2018-10-22 20:22   ` [PATCH 4/8] gettext: #ifdef away GETTEXT POISON-related code from _() and Q_() SZEDER Gábor
2018-10-22 20:22   ` [PATCH 5/8] gettext: put "# GETTEXT POISON #" string literal into a macro SZEDER Gábor
2018-10-22 20:22   ` [PATCH 6/8] gettext: use an enum for the mode of GETTEXT POISONing SZEDER Gábor
2018-10-22 20:22   ` [PATCH 7/8] gettext: introduce GIT_GETTEXT_POISON=scrambled SZEDER Gábor
2018-10-23 14:44     ` Duy Nguyen
2018-10-22 20:22   ` [PATCH 8/8] travis-ci: run GETTEXT POISON build job in scrambled mode, too SZEDER Gábor
2018-10-23 14:37   ` [PATCH] Poison gettext with the Ook language Duy Nguyen
2018-10-27 10:11   ` Jakub Narebski
2018-10-22 20:52 ` Johannes Schindelin
2018-10-22 21:09 ` Ævar Arnfjörð Bjarmason
2018-10-22 21:46   ` Ævar Arnfjörð Bjarmason
2018-10-22 23:04   ` Junio C Hamano
2018-10-23 21:01     ` [PATCH] i18n: make GETTEXT_POISON a runtime option Ævar Arnfjörð Bjarmason
2018-10-24  5:45       ` Junio C Hamano
2018-10-24  7:44         ` Jeff King
2018-10-25  1:00           ` Junio C Hamano
2018-10-25  1:09             ` Jeff King
2018-10-25  1:24               ` Ramsay Jones
2018-10-25 21:23                 ` Jeff King
2018-10-26 19:20                   ` Ævar Arnfjörð Bjarmason
2018-10-27  6:59                     ` Jeff King
2018-10-27 10:42                       ` Ævar Arnfjörð Bjarmason
2018-10-24 11:47         ` [PATCH v2] " Ævar Arnfjörð Bjarmason
2018-11-01 19:31           ` [PATCH v3] " Ævar Arnfjörð Bjarmason
2018-11-02  3:11             ` Junio C Hamano
2018-11-02 16:37             ` SZEDER Gábor
2018-11-08 20:26               ` Ævar Arnfjörð Bjarmason
2018-11-08 20:51                 ` SZEDER Gábor
2018-11-08  3:24             ` Junio C Hamano
2018-11-08 19:12               ` Eric Sunshine
2018-11-08 21:15             ` [PATCH v4 0/2] " Ævar Arnfjörð Bjarmason
2018-11-08 21:15             ` [PATCH v4 1/2] " Ævar Arnfjörð Bjarmason
2018-11-08 21:15             ` [PATCH v4 2/2] Makefile: ease dynamic-gettext-poison transition Ævar Arnfjörð Bjarmason
2018-10-23  9:30   ` [PATCH] Poison gettext with the Ook language Johannes Schindelin
2018-10-23 10:17     ` Ævar Arnfjörð Bjarmason
2018-10-23 11:07       ` Johannes Schindelin
2018-10-23 15:00       ` Duy Nguyen
2018-10-23 16:45         ` Ævar Arnfjörð Bjarmason [this message]
2018-10-24 14:41           ` Duy Nguyen
2018-10-24 17:54             ` Ævar Arnfjörð Bjarmason
2018-10-25  3:52             ` Junio C Hamano
2018-10-25  6:20               ` Jeff King
2018-10-27  6:55                 ` Junio C Hamano

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