Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754365Ab0ATUEO (ORCPT ); Wed, 20 Jan 2010 15:04:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753153Ab0ATUEN (ORCPT ); Wed, 20 Jan 2010 15:04:13 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:42573 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752839Ab0ATUEL (ORCPT ); Wed, 20 Jan 2010 15:04:11 -0500 Subject: [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7 From: Joel Schopp To: Peter Zijlstra Cc: ego@in.ibm.com, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , linux-kernel@vger.kernel.org, benh@kernel.crashing.org In-Reply-To: <1264017638.5717.121.camel@jschopp-laptop> References: <1264017638.5717.121.camel@jschopp-laptop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 20 Jan 2010 14:04:07 -0600 Message-ID: <1264017847.5717.132.camel@jschopp-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2378 Lines: 79 On Power7 processors running in SMT4 mode with 2, 3, or 4 idle threads there is performance benefit to idling the higher numbered threads in the core. This patch implements arch_scale_smt_power to dynamically update smt thread power in these idle cases in order to prefer threads 0,1 over threads 2,3 within a core. Signed-off-by: Joel Schopp --- Index: linux-2.6.git/arch/powerpc/kernel/smp.c =================================================================== --- linux-2.6.git.orig/arch/powerpc/kernel/smp.c +++ linux-2.6.git/arch/powerpc/kernel/smp.c @@ -617,3 +617,44 @@ void __cpu_die(unsigned int cpu) smp_ops->cpu_die(cpu); } #endif + +static inline int thread_in_smt4core(int x) +{ + return x % 4; +} +unsigned long arch_scale_smt_power(struct sched_domain *sd, int cpu) +{ + int cpu2; + int idle_count = 0; + + struct cpumask *cpu_map = sched_domain_span(sd); + + unsigned long weight = cpumask_weight(cpu_map); + unsigned long smt_gain = sd->smt_gain; + + if (cpu_has_feature(CPU_FTRS_POWER7) && weight == 4) { + for_each_cpu(cpu2, cpu_map) { + if (idle_cpu(cpu2)) + idle_count++; + } + + /* the following section attempts to tweak cpu power based + * on current idleness of the threads dynamically at runtime + */ + if (idle_count == 2 || idle_count == 3 || idle_count == 4) { + if (thread_in_smt4core(cpu) == 0 || + thread_in_smt4core(cpu) == 1) { + /* add 75 % to thread power */ + smt_gain += (smt_gain >> 1) + (smt_gain >> 2); + } else { + /* subtract 75 % to thread power */ + smt_gain = smt_gain >> 2; + } + } + } + /* default smt gain is 1178, weight is # of SMT threads */ + smt_gain /= weight; + + return smt_gain; + +} Index: linux-2.6.git/kernel/sched_features.h =================================================================== --- linux-2.6.git.orig/kernel/sched_features.h +++ linux-2.6.git/kernel/sched_features.h @@ -107,7 +107,7 @@ SCHED_FEAT(CACHE_HOT_BUDDY, 1) /* * Use arch dependent cpu power functions */ -SCHED_FEAT(ARCH_POWER, 0) +SCHED_FEAT(ARCH_POWER, 1) SCHED_FEAT(HRTICK, 0) SCHED_FEAT(DOUBLE_TICK, 0) -- 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/