linux-kernel - [PATCH][REPOST] Don't export sched_mc_power_savings on multi-socket single core system

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Message-ID: <4A081A4B.1000204@linux.vnet.ibm.com>
Date:	Mon, 11 May 2009 18:00:03 +0530
From:	Mahesh Jagannath Salgaonkar <mahesh@...ux.vnet.ibm.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
CC:	svaidy@...ux.vnet.ibm.com, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	mahesh@...ux.vnet.ibm.com
Subject: [PATCH][REPOST] Don't export sched_mc_power_savings on multi-socket
  single core system

My previous post got lost somewhere in lkml list. Hence reposting this 
patch again.

Fix to prevent sched_mc_power_saving from being exported through sysfs
for multi-scoket single core system. Max cores should be always greater than
one (1). My earlier patch that introduced fix for not exporting
'sched_mc_power_saving' on laptops  broke it on multi-socket single core
system. This fix addresses issue on both laptop and multi-socket single 
core system.
Below are the Test results:

1. Single socket - multi-core
       Before Patch: Does not export 'sched_mc_power_saving'
       After Patch: Does not export 'sched_mc_power_saving'
       Result: Pass

2. Multi Socket - single core
      Before Patch: exports 'sched_mc_power_saving'
      After Patch: Does not export 'sched_mc_power_saving'
      Result: Pass

3. Multi Socket - Multi core
      Before Patch: exports 'sched_mc_power_saving'
      After Patch: exports 'sched_mc_power_saving'


Signed-off-by: Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>

Index: linux-2.6/arch/x86/include/asm/topology.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/topology.h
+++ linux-2.6/arch/x86/include/asm/topology.h
@@ -203,7 +203,8 @@ struct pci_bus;
  void x86_pci_root_bus_res_quirks(struct pci_bus *b);

  #ifdef CONFIG_SMP
-#define mc_capable()	(cpumask_weight(cpu_core_mask(0)) != nr_cpu_ids)
+#define mc_capable()	(boot_cpu_data.x86_max_cores > 1) && \
+			(cpumask_weight(cpu_core_mask(0)) != nr_cpu_ids)
  #define smt_capable()			(smp_num_siblings > 1)
  #endif
--
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