Path: csiph.com!eternal-september.org!feeder.eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: New and improved version of cdecl
Date: Wed, 29 Oct 2025 21:24:34 -0700
Organization: None to speak of
Lines: 33
Message-ID: <87zf995859.fsf@example.invalid>
References: <87bjlyobts.fsf@example.invalid> <10dkesj$3r64j$1@dont-email.me> <10dl0g9$3venf$1@dont-email.me> <10dmk77$egg1$1@dont-email.me> <10dnprf$qmrg$1@dont-email.me> <10dnsm7$rjo7$1@dont-email.me> <10do23k$u17l$1@dont-email.me> <10dpa4q$1ghgu$1@dont-email.me> <10dq8lr$1tm90$1@dont-email.me> <87zf9azo0m.fsf@example.invalid> <10drip8$2gm7h$1@dont-email.me> <10dteds$30cp7$2@dont-email.me> <10du0gt$37r02$1@dont-email.me> <10du6ic$39mk9$1@dont-email.me> <10dubtm$3bcua$1@dont-email.me> <10dumia$3uier$1@paganini.bofh.team>
MIME-Version: 1.0
Content-Type: text/plain
Injection-Date: Thu, 30 Oct 2025 04:24:36 +0000 (UTC)
Injection-Info: dont-email.me; posting-host="5554a9fe3bce56cb13705adf58e3063f"; logging-data="3621589"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19QqOnc1GCgTGlSuSBO/J5O"
User-Agent: Gnus/5.13 (Gnus v5.13)
Cancel-Lock: sha1:ia9wedsNjAhNZS/0lcLoWLTrmx4= sha1:EeiU4L3m8NpxE7a7CJr0RYzI+54=
Xref: csiph.com comp.lang.c:394956

antispam@fricas.org (Waldek Hebisch) writes:
[...]
> Assuming that you have enough RAM you should try at least using
> 'make -j 3', that is allow make to use up to 3 jobs.  I wrote
> at least, because AFAIK cheapest PC CPU-s of reasonable age
> have at least 2 cores, so to fully utilize the machine you
> need at least 2 jobs.  3 is better, because some jobs may wait
> for I/O.

I haven't been using make's "-j" option for most of my builds.
I'm going to start doing so now (updating my wrapper script).

I initially tried replacing "make" by "make -j", with no numeric
argument.  The result was that my system nearly froze (the load
average went up to nearly 200).  It even invoked the infamous OOM
killer.  "make -j" tells make to use as many parallel processes
as possible.

"make -j $(nproc)" is much better.  The "nproc" command reports the
number of available processing units.  Experiments with a fairly
large build show that arguments to "-j" larger than $(nproc) do
not speed things up (on a fairly old machine with nproc=4).  I had
speculated that "make -n 5" might be worthwhile of some processes
were I/O-bound, but that doesn't appear to be the case.

This applies to GNU make.  There are other "make" implementations
which may or may not have a similar feature.

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */