On Mon, Feb 21 2022, Taylor Blau wrote:
> On Fri, Dec 24, 2021 at 06:37:43PM +0100, Ævar Arnfjörð Bjarmason wrote:
>> $ git -c hyperfine.hook.setup= hyperfine -L rev HEAD~1,HEAD~0 -s 'make -C Documentation man' 'make -C Documentation -j1 man'
>> Benchmark 1: make -C Documentation -j1 man' in 'HEAD~1
>> Time (mean ± σ): 121.7 ms ± 8.8 ms [User: 105.8 ms, System: 18.6 ms]
>> Range (min … max): 112.8 ms … 148.4 ms 26 runs
>>
>> Benchmark 2: make -C Documentation -j1 man' in 'HEAD~0
>> Time (mean ± σ): 97.5 ms ± 8.0 ms [User: 80.1 ms, System: 20.1 ms]
>> Range (min … max): 89.8 ms … 111.8 ms 32 runs
>>
>> Summary
>> 'make -C Documentation -j1 man' in 'HEAD~0' ran
>> 1.25 ± 0.14 times faster than 'make -C Documentation -j1 man' in 'HEAD~1'
>
> Nice speed-up. Though I am not sure I totally understand where it comes
> from ;). Reading 30248886ce8 and the documentation on .SUFFIXES from
> [1], I am still unclear. I guess removing the obsolete built-in suffix
> rules gives make less work to do in general?
I'll update the commit message, but basically the same applies as for
2/8 here (<patch-v2-2.8-b0c9be581a6-20211224T173558Z-avarab@xxxxxxxxx>),
or if you run "make" with "--debug=a". I.e. if before/after this change you do:
git clean -dxf; make -C Documentation/ --debug=a git-status.1 >/tmp/b 2>&1
git clean -dxf; make -C Documentation/ --debug=a git-status.1 >/tmp/a 2>&1
You'll get:
$ wc -l /tmp/[ba]
6515 /tmp/a
144051 /tmp/b
150566 total
Which e.g. for "git-status.txt" starts with (I cut a lot out, there's
way more than this just for that file):
Considering target file 'git-status.txt'.
Looking for an implicit rule for 'git-status.txt'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.o'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.c'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.cc'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.C'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.cpp'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.p'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.f'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.F'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.m'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.r'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.s'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.S'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.mod'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.sh'.
- Trying pattern rule with stem 'git-status.txt'.
- Trying implicit prerequisite 'git-status.txt.o'.
[...]
I.e. given a foo.txt "make" by default will exhaustively consider foo
foo.txt.c, foo.txt.cpp etc. etc.
This is all ultimately a part of make's implicit rule
mechanism. I.e. even if you have no Makefile at all you can run "make
main" if you have a main.c in your directory, and it'll discover it and
compile it with implicit rules, unless you explicitl disable them,
e.g. with "-r":
$ rm Makefile hello; make hello
rm: cannot remove 'Makefile': No such file or directory
rm: cannot remove 'hello': No such file or directory
cc hello.o -o hello
$ rm Makefile hello; make -r hello
rm: cannot remove 'Makefile': No such file or directory
make: *** No rule to make target 'hello'. Stop.
> So long as we're not depending on any of these, this seems like a nice
> little boost to me.
Yes, definitely!
>> diff --git a/shared.mak b/shared.mak
>> index 29f0e69ecb9..155ac84f867 100644
>> --- a/shared.mak
>> +++ b/shared.mak
>> @@ -9,6 +9,11 @@
>> %:: s.%
>> %:: SCCS/s.%
>>
>> +## Likewise delete default $(SUFFIXES). See:
>> +##
>> +## info make --index-search=.DELETE_ON_ERROR
>> +.SUFFIXES:
>
> Hmm. s/DELETE_ON_ERROR/SUFFIXES? Or perhaps I'm holding this whole thing
> incorrectly:
>
> ~/s/git [nand] (ab/make-noop) $ info make --index-search=.DELETE_ON_ERROR
> no index entries found for '.DELETE_ON_ERROR'
> ~/s/git [nand] (ab/make-noop) $ info make --index-search=.SUFFIXES
> no index entries found for '.SUFFIXES'
Yes that's a copy/paste error, it should be .SUFFIXES.
But both commands should work, or emit an error like:
$ info doesnotexist --index-search=.DELETE_ON_ERROR
info: No menu item 'doesnotexist' in node '(dir)Top'
A broken OS package? Self-built "make"?
In any case I could also link to
https://www.gnu.org/software/make/manual/html_node/Suffix-Rules.html;
which is the same information online (but may not match your local
"make" version)>
