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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v3 6/6] Makefile: build "$(FUZZ_OBJS)" in CI, not under "all"
Date: Sun, 28 Feb 2021 21:13:54 +0100	[thread overview]
Message-ID: <87wnusj6gt.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <YDVJZnmTiBYZ4iPM@coredump.intra.peff.net>


On Tue, Feb 23 2021, Jeff King wrote:

> On Tue, Feb 23, 2021 at 12:41:32PM +0100, Ævar Arnfjörð Bjarmason wrote:
>
>> Adding $(FUZZ_OBJS) as a dependency on "all" was intentionally done in
>> 5e472150800 (fuzz: add basic fuzz testing target., 2018-10-12).
>> 
>> Rather than needlessly build these objects which aren't required for
>> the build every time we make "all", let's instead move them to be
>> built by the CI jobs.
>> 
>> The goal is to make sure that we don't inadvertently break these, we
>> can accomplish that goal by building them in CI, rather than slowing
>> down every build of git for everyone everywhere.
>
> The current state is that regular devs are responsible for avoiding
> compile breakages in the fuzz objects, even if they don't care
> themselves. Your earlier patches turned this into: regular devs are not
> on the hook for breaking fuzz objects; they are the responsibility of
> fuzz people. I'm OK with either of those, but this approach seems to me
> like the worst of both worlds. ;)
>
> If you do a refactor, you are still on the hook for breaking the fuzz
> objects because CI will fail (and you have to investigate it, and fix it
> for CI to remain a useful tool). But instead of finding out about the
> problem quickly as you're working, instead you push up what you think is
> a finished result, and then from minutes to hours later you get a
> notification telling you that oops, you missed a spot. I find that the
> shorter the error-fix-compile cycle is, the less time I waste waiting or
> context-switching.
>
> If we had a ton of fuzz object files that took forever to build, the
> savings on each build might be worth it. But AFAICT (from timing "make
> clean; make -j1" before and after), we are saving less than 1% of the
> build time (which is way less than the run-to-run noise).
>
> It doesn't seem like the right tradeoff to me. (Likewise, if other
> CI-only checks we have, like coccinelle, could be run at a similar cost,
> I'd recommend sticking them into the default developer build).

It's mainly psychological and doesn't contribute much to overall build
time as a percentage, but I find it grating that the last thing I see
before I switch away from that terminal when firing off a build on a
slower GCC farm box I can only use -j1 on, is these fuzz objects taking
2-3 seconds to build, knowing I'm wasting time on something I'll never
need.

I think when we build something we should narrowly be compiling only the
things we need, not running some sort of pseudo-CI on every developer's
computer. We can have CI or other targets for that.

Besides, if we were going for some sane cost-benefit here we'd have
targets to try compiling with NO_CURL=1 or some other conditional setups
that are actually common in the wild.

> One thing we _could_ do is stop building fuzz objects as part of "all",
> but include them for DEVELOPER=1 builds (which includes CI). That keeps
> them from hurting normal users (who don't actually need them), but
> prevents bitrot. It doesn't address your original motivation though (you
> as a developer would probably still be building them).

Please no. A very good thing about how DEVELOPER=1 works is that we're
not doing anything extra except advisory compilation flags. It's turned
on for "production" builds in a lot of settings because of that.

It would also be very annoying to e.g. have some failure on Solaris or
whatever, debug it with DEVELOPER=1, and then get some completely
unrelated failure in the developer-only code, e.g. because we'd decided
to compile all of fuzz/NO_OPENSSL/NO_CURL etc. and had some bug there.

Yes that bug would be worthwhile to fix, but not right there and
then. So having it under some "make all-combinations" flag or whatever
would be better.

  parent reply	other threads:[~2021-02-28 20:14 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-26 16:07 [PATCH 0/4] Makefile: micro-optimize light non-test builds Ævar Arnfjörð Bjarmason
2021-01-26 16:07 ` [PATCH 1/4] Makefile: refactor assignment for subsequent change Ævar Arnfjörð Bjarmason
2021-01-27  1:29   ` Junio C Hamano
2021-01-26 16:07 ` [PATCH 2/4] Makefile: refactor " Ævar Arnfjörð Bjarmason
2021-01-26 16:07 ` [PATCH 3/4] Makefile: add a NO_TEST_TOOLS flag Ævar Arnfjörð Bjarmason
2021-01-26 16:07 ` [PATCH 4/4] Makefile: add a NO_{INSTALL_,}SCRIPT_FALLBACKS target Ævar Arnfjörð Bjarmason
2021-01-26 21:16 ` [PATCH 0/4] Makefile: micro-optimize light non-test builds Jeff King
2021-01-27  1:38   ` Junio C Hamano
2021-01-27  4:34     ` Jeff King
2021-01-27  6:07       ` Junio C Hamano
2021-01-28 18:23   ` [PATCH 0/6] Makefile: add {program,xdiff,test,git}-objs & objects targets Ævar Arnfjörð Bjarmason
2021-02-01 11:17     ` [PATCH v2 " Ævar Arnfjörð Bjarmason
2021-02-03  1:11       ` Junio C Hamano
2021-02-04  7:06         ` Jeff King
2021-02-04 17:49           ` Junio C Hamano
2021-02-23 11:41       ` [PATCH v3 0/6] Makefile: add {program,xdiff,test,git,fuzz}-objs " Ævar Arnfjörð Bjarmason
2021-02-23 17:57         ` Junio C Hamano
2021-02-23 18:31         ` Jeff King
2021-02-23 11:41       ` [PATCH v3 1/6] Makefile: guard against TEST_OBJS in the environment Ævar Arnfjörð Bjarmason
2021-02-23 11:41       ` [PATCH v3 2/6] Makefile: split up long OBJECTS line Ævar Arnfjörð Bjarmason
2021-02-23 11:41       ` [PATCH v3 3/6] Makefile: sort OBJECTS assignment for subsequent change Ævar Arnfjörð Bjarmason
2021-02-23 11:41       ` [PATCH v3 4/6] Makefile: split OBJECTS into OBJECTS and GIT_OBJS Ævar Arnfjörð Bjarmason
2021-02-23 11:41       ` [PATCH v3 5/6] Makefile: add {program,xdiff,test,git,fuzz}-objs & objects targets Ævar Arnfjörð Bjarmason
2021-02-23 11:41       ` [PATCH v3 6/6] Makefile: build "$(FUZZ_OBJS)" in CI, not under "all" Ævar Arnfjörð Bjarmason
2021-02-23 18:28         ` Jeff King
2021-02-23 19:19           ` Junio C Hamano
2021-02-28 20:13           ` Ævar Arnfjörð Bjarmason [this message]
2021-03-01  9:39             ` Jeff King
2021-02-01 11:17     ` [PATCH v2 1/6] Makefile: remove "all" on "$(FUZZ_OBJS)" Ævar Arnfjörð Bjarmason
2021-02-04  6:51       ` Jeff King
2021-02-01 11:17     ` [PATCH v2 2/6] Makefile: guard against TEST_OBJS in the environment Ævar Arnfjörð Bjarmason
2021-02-01 11:17     ` [PATCH v2 3/6] Makefile: split up long OBJECTS line Ævar Arnfjörð Bjarmason
2021-02-01 11:17     ` [PATCH v2 4/6] Makefile: sort OBJECTS assignment for subsequent change Ævar Arnfjörð Bjarmason
2021-02-01 11:17     ` [PATCH v2 5/6] Makefile: split OBJECTS into OBJECTS and GIT_OBJS Ævar Arnfjörð Bjarmason
2021-02-01 11:17     ` [PATCH v2 6/6] Makefile: add {program,xdiff,test,git}-objs & objects targets Ævar Arnfjörð Bjarmason
2021-02-01 22:30       ` Junio C Hamano
2021-01-28 18:23   ` [PATCH 1/6] Makefile: remove "all" on "$(FUZZ_OBJS)" Ævar Arnfjörð Bjarmason
2021-01-28 18:23   ` [PATCH 2/6] Makefile: guard against TEST_OBJS in the environment Ævar Arnfjörð Bjarmason
2021-01-29  7:49     ` Junio C Hamano

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