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

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Date:	Thu, 23 Apr 2015 08:16:15 -0600
From:	David Ahern <david.ahern@...cle.com>
To:	Will Deacon <will.deacon@....com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Rutland <Mark.Rutland@....com>,
	"jolsa@...nel.org" <jolsa@...nel.org>,
	"namhyung@...nel.org" <namhyung@...nel.org>,
	"acme@...hat.com" <acme@...hat.com>
Subject: Re: arm/arm64 perf build issue with mainline

On 4/23/15 8:04 AM, Will Deacon wrote:
>  From 28740111e81aa9247bf48e3125dc43cc31d94e6f Mon Sep 17 00:00:00 2001
> From: Will Deacon <will.deacon@....com>
> Date: Thu, 23 Apr 2015 15:00:16 +0100
> Subject: [PATCH] tools: perf: use getconf to determine number of online CPUs
>
> Parsing /proc/cpuinfo is a fiddly, arch-dependent business anda recent
> change to get it working for Sparc broke arm and arm64 platforms.
>
> Instead, use sysconf to determine the number of online CPUs and avoid
> parsing /proc/cpuinfo entirely.
>
> Signed-off-by: Will Deacon <will.deacon@....com>
> ---
>   tools/perf/Makefile | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index c699dc35eef9..c26cb04ce6bd 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -24,7 +24,7 @@ unexport MAKEFLAGS
>   # (To override it, run 'make JOBS=1' and similar.)
>   #
>   ifeq ($(JOBS),)
> -  JOBS := $(shell egrep -c '^processor|^CPU' /proc/cpuinfo 2>/dev/null)
> +  JOBS := $(shell getconf _NPROCESSORS_ONLN 2>/dev/null)
>     ifeq ($(JOBS),0)
>       JOBS := 1
>     endif
>

Certainly a more robust way of doing it but I am concerned this might 
end up breaking others. For Fedora at least getconf is in the 
glibc-common package and there are users that do not build with glibc. 
It is not clear if the build system for those environments will have 
getconf.
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