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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Jeff King <peff@peff.net>
Cc: "Taylor Blau" <me@ttaylorr.com>,
	git@vger.kernel.org, "Junio C Hamano" <gitster@pobox.com>,
	"Johannes Sixt" <j6t@kdbg.org>,
	"Øystein Walle" <oystwa@gmail.com>
Subject: Re: [PATCH 0/8] Makefile: make command-list.h 2-5x as fast with -jN
Date: Fri, 22 Oct 2021 12:51:11 +0200	[thread overview]
Message-ID: <211022.86h7d9kzgt.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <YXF6Wwcvc0vq5ADZ@coredump.intra.peff.net>


On Thu, Oct 21 2021, Jeff King wrote:

> On Thu, Oct 21, 2021 at 02:48:24AM +0200, Ævar Arnfjörð Bjarmason wrote:
>
>> >> There's subtle dependency issues there as well, and just having a
>> >> one-off solution for the the command-list.h doesn't get us closer to
>> >> addressing that sibling implementation.
>> >
>> > So I don't know what "subtle dependency issues" you found here, but this
>> > is exactly the kind of complexity it was my goal to avoid.
>> 
>> But how? I don't see how narrowly making the loop in generate-cmdlist.sh
>> gets us closer to generating the "cmds_txt" in the
>> Documentation/Makefile.
>
> What I meant is that the work to get everything right in the Makefile to
> correctly handle dependencies and a partial rebuild can be tricky. For
> instance, you're still stuck with a big wildcard dependency on
> Documentation/git*.txt (and a manual list of exclusions in the Makefile)
> because it's hard in make to do make new dynamic rules based on an
> existing one (i.e., the list _should_ come from what's in
> command-list.txt). Or the fact that we apparently need to keep the old
> script around or cmake anyway.
>
> It's also much slower. Here are from-scratch builds before and after
> your patch 7:
>
>   $ hyperfine --warmup 1 -p 'make clean' 'make command-list.h'
>   Benchmark #1: make command-list.h
>     Time (mean ± σ):      1.527 s ±  0.060 s    [User: 1.320 s, System: 0.649 s]
>     Range (min … max):    1.433 s …  1.625 s    10 runs
>    
>   
>   $ hyperfine --warmup 1 -p 'make clean' 'make command-list.h'
>   Benchmark #1: make command-list.h
>     Time (mean ± σ):      2.661 s ±  0.080 s    [User: 2.359 s, System: 1.082 s]
>     Range (min … max):    2.481 s …  2.756 s    10 runs
>
> I know that partial builds will offset that in some cases, but it still
> feels like a step in the wrong direction. Even with a partial build,
> swapping out "make clean" for "touch Documentation/git-add.txt" takes
> about 200ms for me. Whereas with the faster version of
> generate-cmdlist.sh I showed, it takes 150ms.
>
> Now performance isn't everything, and it's possible these partial
> snippets will be useful in other places. But I'm not sure I see any real
> advantage in this series, and it seems like we're taking a hit in both
> performance and complexity in the meantime.

Yes, the same numbers are noted in the 7/8 commit message. I.e. it's
slower on -j1, but faster with higher -j<n> numbers.

Aside from any changes I'm proposing here it seems rather pointless to
me to optimize the runtime of -j1 runs.

I think we use those in e.g. CI, so of course if they become *really*
slow it will matter, but the purpose of this change is to make hacking
on git easier, both in terms of runtime and discovering what the
Makefile is doing wih V=1.

I think anyone hacking on git is going to be on a system with -j2 at
least. So again, separate from these specific changes, if we've got a
change that speeds up -jN runs at the cost of a -j1 run that seems like
good thing.

In terms of the utility of benchmarks this benchmark uses "make" and is
meaningful, but e.g. <YXCKqAEwtwFozWk6@nand.local> (and I think some
other ones?) in this thread invoke the shellscript directly.

Those sorts of benchmarks may or may not matter, and in this case the
script is always called in the context of a Makefile, so that's really
the only meaningful way to test it. If e.g. its performance changes in a
way that won't be noticed in other Makefile noise it probably won't
matter to anyone.


  parent reply	other threads:[~2021-10-22 12:37 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 13:16 Why the Makefile is so eager to re-build & re-link Ævar Arnfjörð Bjarmason
2021-06-24 15:16 ` Jeff King
2021-06-24 15:28   ` Ævar Arnfjörð Bjarmason
2021-06-24 21:30   ` Johannes Sixt
2021-06-25  8:34     ` Ævar Arnfjörð Bjarmason
2021-06-25  9:01       ` Ævar Arnfjörð Bjarmason
2021-06-29  2:13       ` Jeff King
2021-10-20 18:39         ` [PATCH 0/8] Makefile: make command-list.h 2-5x as fast with -jN Ævar Arnfjörð Bjarmason
2021-10-20 18:39           ` [PATCH 1/8] command-list.txt: sort with "LC_ALL=C sort" Ævar Arnfjörð Bjarmason
2021-10-20 18:39           ` [PATCH 2/8] generate-cmdlist.sh: trivial whitespace change Ævar Arnfjörð Bjarmason
2021-10-20 18:39           ` [PATCH 3/8] generate-cmdlist.sh: spawn fewer processes Ævar Arnfjörð Bjarmason
2021-10-20 18:39           ` [PATCH 4/8] generate-cmdlist.sh: don't call get_categories() from category_list() Ævar Arnfjörð Bjarmason
2021-10-20 18:39           ` [PATCH 5/8] generate-cmdlist.sh: run "grep | sort", not "sort | grep" Ævar Arnfjörð Bjarmason
2021-10-20 18:39           ` [PATCH 6/8] generate-cmdlist.sh: replace for loop by printf's auto-repeat feature Ævar Arnfjörð Bjarmason
2021-10-21 14:42             ` Jeff King
2021-10-21 16:25               ` Jeff King
2021-10-20 18:39           ` [PATCH 7/8] Makefile: stop having command-list.h depend on a wildcard Ævar Arnfjörð Bjarmason
2021-10-21 14:45             ` Jeff King
2021-10-21 18:24               ` Junio C Hamano
2021-10-21 22:46             ` Øystein Walle
2021-10-20 18:39           ` [PATCH 8/8] Makefile: assert correct generate-cmdlist.sh output Ævar Arnfjörð Bjarmason
2021-10-20 20:35           ` [PATCH 0/8] Makefile: make command-list.h 2-5x as fast with -jN Jeff King
2021-10-20 21:31             ` Taylor Blau
2021-10-20 23:14               ` Ævar Arnfjörð Bjarmason
2021-10-20 23:46                 ` Jeff King
2021-10-21  0:48                   ` Ævar Arnfjörð Bjarmason
2021-10-21  2:20                     ` Taylor Blau
2021-10-22 12:37                       ` Ævar Arnfjörð Bjarmason
2021-10-21 14:34                     ` Jeff King
2021-10-21 22:34                       ` Junio C Hamano
2021-10-22 10:51                       ` Ævar Arnfjörð Bjarmason [this message]
2021-10-22 18:31                         ` Jeff King
2021-10-22 20:50                           ` Ævar Arnfjörð Bjarmason
2021-10-21  5:39                 ` Eric Sunshine
2021-10-22 19:36           ` [PATCH v2 00/10] Makefile: make generate-cmdlist.sh much faster Ævar Arnfjörð Bjarmason
2021-10-22 19:36             ` [PATCH v2 01/10] command-list.txt: sort with "LC_ALL=C sort" Ævar Arnfjörð Bjarmason
2021-10-25 18:29               ` Junio C Hamano
2021-10-25 21:22                 ` Ævar Arnfjörð Bjarmason
2021-10-25 21:26                   ` Junio C Hamano
2021-10-22 19:36             ` [PATCH v2 02/10] generate-cmdlist.sh: trivial whitespace change Ævar Arnfjörð Bjarmason
2021-10-22 19:36             ` [PATCH v2 03/10] generate-cmdlist.sh: spawn fewer processes Ævar Arnfjörð Bjarmason
2021-10-22 19:36             ` [PATCH v2 04/10] generate-cmdlist.sh: don't call get_categories() from category_list() Ævar Arnfjörð Bjarmason
2021-10-22 19:36             ` [PATCH v2 05/10] generate-cmdlist.sh: run "grep | sort", not "sort | grep" Ævar Arnfjörð Bjarmason
2021-10-22 19:36             ` [PATCH v2 06/10] generate-cmdlist.sh: replace for loop by printf's auto-repeat feature Ævar Arnfjörð Bjarmason
2021-10-22 19:36             ` [PATCH v2 07/10] generate-cmdlist.sh: stop sorting category lines Ævar Arnfjörð Bjarmason
2021-10-25 16:39               ` Jeff King
2021-10-22 19:36             ` [PATCH v2 08/10] generate-cmdlist.sh: do not shell out to "sed" Ævar Arnfjörð Bjarmason
2021-10-25 16:46               ` Jeff King
2021-10-25 17:52                 ` Jeff King
2021-10-22 19:36             ` [PATCH v2 09/10] generate-cmdlist.sh: replace "grep' invocation with a shell version Ævar Arnfjörð Bjarmason
2021-10-23 22:19               ` Junio C Hamano
2021-10-23 22:26               ` Junio C Hamano
2021-10-22 19:36             ` [PATCH v2 10/10] generate-cmdlist.sh: replace "cut", "tr" and "grep" with pure-shell Ævar Arnfjörð Bjarmason
2021-10-23 22:26               ` Junio C Hamano
2021-10-22 21:20             ` [PATCH v2 00/10] Makefile: make generate-cmdlist.sh much faster Taylor Blau
2021-10-23 22:34             ` Junio C Hamano
2021-10-25 16:57             ` Jeff King
2021-11-05 14:07             ` [PATCH v3 00/10] generate-cmdlist.sh: make it (and "make") run faster Ævar Arnfjörð Bjarmason
2021-11-05 14:07               ` [PATCH v3 01/10] command-list.txt: sort with "LC_ALL=C sort" Ævar Arnfjörð Bjarmason
2021-11-05 22:45                 ` Junio C Hamano
2021-11-06  4:26                   ` Ævar Arnfjörð Bjarmason
2021-11-08 19:18                     ` Junio C Hamano
2021-11-05 14:08               ` [PATCH v3 02/10] generate-cmdlist.sh: trivial whitespace change Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 03/10] generate-cmdlist.sh: spawn fewer processes Ævar Arnfjörð Bjarmason
2021-11-05 22:47                 ` Junio C Hamano
2021-11-06  4:23                   ` Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 04/10] generate-cmdlist.sh: don't call get_categories() from category_list() Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 05/10] generate-cmdlist.sh: run "grep | sort", not "sort | grep" Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 06/10] generate-cmdlist.sh: replace for loop by printf's auto-repeat feature Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 07/10] generate-cmdlist.sh: stop sorting category lines Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 08/10] generate-cmdlist.sh: do not shell out to "sed" Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 09/10] generate-cmdlist.sh: replace "grep' invocation with a shell version Ævar Arnfjörð Bjarmason
2021-11-05 14:08               ` [PATCH v3 10/10] generate-cmdlist.sh: don't parse command-list.txt thrice Ævar Arnfjörð Bjarmason
2021-06-25 21:17   ` Why the Makefile is so eager to re-build & re-link Felipe Contreras
2021-06-29  5:04   ` Eric Sunshine
2021-06-24 23:35 ` Øystein Walle
2021-06-24 23:39   ` Øystein Walle
2021-06-25  0:11   ` Ævar Arnfjörð Bjarmason
2021-07-02 11:58 ` [PATCH] Documentation/Makefile: don't re-build on 'git version' changes Ævar Arnfjörð Bjarmason
2021-07-02 15:53   ` Junio C Hamano
2021-07-03 11:58     ` Ævar Arnfjörð Bjarmason
2021-07-05 19:48       ` Junio C Hamano
2021-07-03  1:05   ` Felipe Contreras
2021-07-03 12:03     ` Ævar Arnfjörð Bjarmason
2021-07-03 18:56       ` Felipe Contreras
2021-07-05 19:38       ` Junio C Hamano
2021-07-06 22:25         ` Felipe Contreras

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