Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752388Ab2FMJW5 (ORCPT ); Wed, 13 Jun 2012 05:22:57 -0400 Received: from mail-ob0-f174.google.com ([209.85.214.174]:37560 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751306Ab2FMJW4 convert rfc822-to-8bit (ORCPT ); Wed, 13 Jun 2012 05:22:56 -0400 MIME-Version: 1.0 In-Reply-To: References: <1339502524-10265-1-git-send-email-vincent.guittot@linaro.org> <1339502524-10265-2-git-send-email-vincent.guittot@linaro.org> Date: Wed, 13 Jun 2012 11:22:56 +0200 Message-ID: Subject: Re: [RFC 1/4] ARM: topology: Add arch_scale_freq_power function From: Vincent Guittot To: Jean Pihet Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org, devicetree-discuss@lists.ozlabs.org, linux@arm.linux.org.uk, peterz@infradead.org, grant.likely@secretlab.ca, rob.herring@calxeda.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2703 Lines: 72 On 13 June 2012 10:50, Jean Pihet wrote: > Hi Vincent, > > On Tue, Jun 12, 2012 at 2:02 PM, Vincent Guittot > wrote: >> Add infrastructure to be able to modify the cpu_power of each core >> >> Signed-off-by: Vincent Guittot >> --- >> ?arch/arm/include/asm/topology.h | ? ?2 ++ >> ?arch/arm/kernel/topology.c ? ? ?| ? 36 +++++++++++++++++++++++++++++++++++- >> ?2 files changed, 37 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h >> index 58b8b84..78e4c85 100644 >> --- a/arch/arm/include/asm/topology.h >> +++ b/arch/arm/include/asm/topology.h >> @@ -27,11 +27,13 @@ void init_cpu_topology(void); >> ?void store_cpu_topology(unsigned int cpuid); >> ?const struct cpumask *cpu_coregroup_mask(int cpu); >> >> +void set_power_scale(unsigned int cpu, unsigned long power); >> ?#else >> >> ?static inline void init_cpu_topology(void) { } >> ?static inline void store_cpu_topology(unsigned int cpuid) { } >> >> +static inline void set_power_scale(unsigned int cpu, unsigned long power) { } >> ?#endif >> >> ?#include >> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c >> index 8200dea..00301a7 100644 >> --- a/arch/arm/kernel/topology.c >> +++ b/arch/arm/kernel/topology.c >> @@ -22,6 +22,35 @@ >> ?#include >> ?#include >> >> +/* >> + * cpu power scale management >> + */ >> + >> +/* >> + * cpu power table >> + * This per cpu data structure describes the relative capacity of each core. >> + * On a heteregenous system, cores don't have the same computation capacity >> + * and we reflect that difference in the cpu_power field so the scheduler can >> + * take this difference into account for load balance. A per cpu structure is >> + * preferred because each cpu is mainly using its own cpu_power even it's not >> + * always true because of nohz_idle_balance > The end of the comment is unclear IMO; Can you give more details on > the relation between cpu_power and nohz_idle_balance? When several cores are idle, one core runs the load balance for all idle cores. The update of the cpu_power can be done during rebalance and arch_scale_freq_power can be called by CPU0 for updating the cpu_power of CPU1. I was probably not clear enough in my first explanation. I will reword the comment Regards, Vincent > > Regards, > Jean -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/