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From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Huth <thuth@redhat.com>, qemu-devel@nongnu.org
Cc: alex.bennee@linaro.org
Subject: Re: [PATCH 2/3] ci: do not use #processors+1 jobs, #processors is enough
Date: Tue, 18 May 2021 14:30:04 +0200	[thread overview]
Message-ID: <7155c55a-1566-d7f0-d59e-ee48707302cf@redhat.com> (raw)
In-Reply-To: <40f9d46b-d234-c029-3ba2-f5dcac8b87fc@redhat.com>

On 18/05/21 12:49, Thomas Huth wrote:
>>
>> -    - JOBS=$(expr $(nproc) + 1)
>> +    - JOBS=$(nproc || echo 1)
> 
> The basic idea of the "+ 1" was to make sure that there is always a 
> thread that runs on a CPU while maybe another one is waiting for I/O to 
> complete.

Ah, I see.  It doesn't make much sense for "make check" jobs however, 
which is where I wanted to get with the next patch.

I'm not sure it's even true anymore with current build machines (which 
tend to have a large buffer cache for headers) and optimizing compilers 
that compilation is I/O bound, so I'll time the two and see if there is 
an actual difference.

Paolo

  This is suggested by various sites on the web, e.g.:
> 
> https://unix.stackexchange.com/questions/519092/what-is-the-logic-of-using-nproc-1-in-make-command 
> 
> So not sure whether this patch here make sense ... I'd rather drop it.



  reply	other threads:[~2021-05-18 12:34 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-18  8:41 [PATCH 0/3] Small CI improvements Paolo Bonzini
2021-05-18  8:41 ` [PATCH 1/3] cirrus-ci: test installation Paolo Bonzini
2021-05-18 13:50   ` Alex Bennée
2021-05-19 14:44     ` Paolo Bonzini
2021-05-18  8:41 ` [PATCH 2/3] ci: do not use #processors+1 jobs, #processors is enough Paolo Bonzini
2021-05-18  8:56   ` Philippe Mathieu-Daudé
2021-05-18 10:49   ` Thomas Huth
2021-05-18 12:30     ` Paolo Bonzini [this message]
2021-05-18 12:43       ` Daniel P. Berrangé
2021-05-18 12:48         ` Paolo Bonzini
2021-05-18  8:41 ` [PATCH 3/3] ci: add -j to all "make" jobs Paolo Bonzini
2021-05-18  8:58   ` Philippe Mathieu-Daudé
2021-05-19 15:28 ` [PATCH 0/3] Small CI improvements Alex Bennée

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