linux-kernel - Re: [Q] perf, x86: should perf_event

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Message-ID: <20100529130254.GH5322@lenovo>
Date:	Sat, 29 May 2010 17:02:54 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Q] perf, x86: should perf_event_x.c being compiled
	conditionally?

On Sat, May 29, 2010 at 09:38:57AM +0200, Peter Zijlstra wrote:
> On Sat, 2010-05-29 at 01:35 +0400, Cyrill Gorcunov wrote:
> > Hi,
> > 
> > while was building the kernel for pretty old laptop I've noticed
> > that perf_event_x.c depends on CONFIG_CPU_SUP_ only. So I'm somehow
> > confused. Should not some additional condition being used?
> > 
> > For example if a person have Core 2 or Nehalem machine, he will
> > definitely not need p6 and p4 events (yes, they are not _that_ big
> > in size, but anyway).
> > 
> > On the other hands distro builders would prefer to have all compiled in.
> > 
> > Not sure about what is the best way to resolve this, but perhaps I'm just
> > missing some key moment?
> 
> We had to split out on the CPU_SUP_* stuff because the AMD support
> relies on symbols otherwise not present.
> 
> So fixing build dependencies is the main reason we have that.
> 
> If you want to extend it, feel free, but be sure to test the
> full .config space ;-)
> 

Thanks for explanation. I guess we may have something like below.
Note that I didn't squeeze into *.c files, only Kconfig is touched
so that we get "Processor type and features" -> "Supported Perfomance
Events" menu. All entries are "Y" by default and depends on
PERF_EVENTS && CPU_SUP_INTEL (since we have this trick for Intel
cpus only at moment). Just an idea.

	-- Cyrill
---
 arch/x86/Kconfig.cpu      |    4 ++++
 arch/x86/Kconfig.cpu.perf |   31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

Index: linux-2.6.git/arch/x86/Kconfig.cpu
=====================================================================
--- linux-2.6.git.orig/arch/x86/Kconfig.cpu
+++ linux-2.6.git/arch/x86/Kconfig.cpu
@@ -506,3 +506,7 @@ config CPU_SUP_UMC_32
 	  CPU might render the kernel unbootable.
 
 	  If unsure, say N.
+
+#
+# Performance event specifics
+source "arch/x86/Kconfig.cpu.perf"
Index: linux-2.6.git/arch/x86/Kconfig.cpu.perf
=====================================================================
--- /dev/null
+++ linux-2.6.git/arch/x86/Kconfig.cpu.perf
@@ -0,0 +1,31 @@
+if PERF_EVENTS && CPU_SUP_INTEL
+menu "Supported Performance Events"
+
+config PERF_EVENTS_INTEL
+	bool "Intel Architectural Performance Events"
+	default y
+	---help---
+	  Intel Architectural Performance Events (Architectural PerfMon version 2
+	  and later). Includes support for Core/Core2/Atom/Nehalem CPU families.
+
+	  If unsure say Y.
+
+config PERF_EVENTS_INTEL_NETBURST
+	bool "Netburst Performance Events"
+	default y
+	---help---
+	  Netburst family performance events (Pentium 4, old Xeons).
+
+	  If unsure say Y.
+
+config PERF_EVENTS_INTEL_P6
+	bool "P6 family Performance Events"
+	default y
+	---help---
+	  P6 family performance events (Pentium Pro, Pentium II,
+	  Pentium III, Pentium M).
+
+	  If unsure say Y.
+
+endmenu
+endif
--
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