linux-kernel - Re: arm/arm64 perf build issue with mainline

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Date:	Thu, 23 Apr 2015 08:29:16 -0600
From:	David Ahern <david.ahern@...cle.com>
To:	Will Deacon <will.deacon@....com>, Ingo Molnar <mingo@...nel.org>
CC:	linux-kernel@...r.kernel.org, mark.rutland@....com,
	jolsa@...nel.org, namhyung@...nel.org, acme@...hat.com
Subject: Re: arm/arm64 perf build issue with mainline

On 4/23/15 5:29 AM, Will Deacon wrote:
> Hi all,
>
> Commit 6428c59a97de ("perf tools: Set JOBS based on CPU or processor")
> causes weird behaviour on arm/arm64 platforms because we use the "CPU"
> prefix for things like:
>
> CPU implementer : 0x41
> CPU architecture: 8
> CPU variant     : 0x0
> CPU part        : 0xd03
> CPU revision    : 0
>
> in /proc/cpuinfo. Consequently, a 6 core machine ends up doing:
>
> will@...finement-loaf:~/linux/tools/perf$ make
>    BUILD:   Doing 'make -j36' parallel build
>
> which is a little overwhelming. Any chance we can predicate the extra
> part of the regex on $(ARCH) being sparc?


Frankly, I think the JOBS parameter needs to be removed. It's 
non-standard way of controlling parallelism in the build and it makes 
the assumption that if a system has N processors all of those can be 
used to build perf which is not true if you are building perf as part of 
bigger image builds -- like Yocto for example.

Ingo: As I recall you put this in? Opinions on removing it? Users can 
always add the standard '-j N' for parallelism just like they do for 
kernel builds.

David
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