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

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Message-ID: <20150423140454.GJ1652@arm.com>
Date:	Thu, 23 Apr 2015 15:04:54 +0100
From:	Will Deacon <will.deacon@....com>
To:	"david.ahern@...cle.com" <david.ahern@...cle.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 Thu, Apr 23, 2015 at 12:29:16PM +0100, 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?

Scratch that, how about using sysconf instead? Patch below...

Will

--->8

>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
-- 
2.1.4

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