linux-kernel - [tip:sched/core] sched: Don't export sched_mc_power_savings on multi-socket single core system

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Message-ID: <tip-33faf60cb97fee37b0e60a68c171f9099c576dec@git.kernel.org>
Date:	Mon, 11 May 2009 15:09:51 GMT
From:	tip-bot for Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, venkatesh.pallipadi@...el.com,
	mahesh@...ux.vnet.ibm.com, suresh.b.siddha@...el.com,
	tglx@...utronix.de, mingo@...e.hu, svaidy@...ux.vnet.ibm.com
Subject: [tip:sched/core] sched: Don't export sched_mc_power_savings on multi-socket single core system

Commit-ID:  33faf60cb97fee37b0e60a68c171f9099c576dec
Gitweb:     http://git.kernel.org/tip/33faf60cb97fee37b0e60a68c171f9099c576dec
Author:     Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
AuthorDate: Mon, 11 May 2009 20:09:14 +0530
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Mon, 11 May 2009 17:05:57 +0200

sched: Don't export sched_mc_power_savings on multi-socket single core system

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'

[ Impact: make the sched_mc_power_saving control available more consistently ]

Signed-off-by: Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>
Cc: Suresh B Siddha <suresh.b.siddha@...el.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <20090511143914.GB4853@...shya.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 arch/x86/include/asm/topology.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index f44b49a..066ef59 100644
--- a/arch/x86/include/asm/topology.h
+++ b/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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