Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757563Ab0BEU6g (ORCPT ); Fri, 5 Feb 2010 15:58:36 -0500 Received: from e33.co.us.ibm.com ([32.97.110.151]:45271 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755424Ab0BEU6d (ORCPT ); Fri, 5 Feb 2010 15:58:33 -0500 Subject: [PATCHv4 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, jschopp@austin.ibm.com In-Reply-To: <1264721088.10385.1.camel@jschopp-laptop> References: <1264017638.5717.121.camel@jschopp-laptop> <1264017847.5717.132.camel@jschopp-laptop> <1264548495.12239.56.camel@jschopp-laptop> <1264720855.9660.22.camel@jschopp-laptop> <1264721088.10385.1.camel@jschopp-laptop> Content-Type: text/plain; charset="UTF-8" Date: Fri, 05 Feb 2010 14:57:58 -0600 Message-ID: <1265403478.6089.41.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: 3424 Lines: 105 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 --- Version 3 adds the #ifdef to avoid compiling on kernels that don't need it 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 @@ -620,3 +620,61 @@ void __cpu_die(unsigned int cpu) smp_ops->cpu_die(cpu); } #endif + +#ifdef CONFIG_SCHED_SMT +unsigned long arch_scale_smt_power(struct sched_domain *sd, int cpu) +{ + int sibling; + int idle_count = 0; + int thread; + + /* Setup the default weight and smt_gain used by most cpus for SMT + * Power. Doing this right away covers the default case and can be + * used by cpus that modify it dynamically. + */ + struct cpumask *sibling_map = sched_domain_span(sd); + unsigned long weight = cpumask_weight(sibling_map); + unsigned long smt_gain = sd->smt_gain; + + + if (cpu_has_feature(CPU_FTR_ASYNC_SMT4) && weight == 4) { + for_each_cpu(sibling, sibling_map) { + if (idle_cpu(sibling)) + idle_count++; + } + + /* the following section attempts to tweak cpu power based + * on current idleness of the threads dynamically at runtime + */ + if (idle_count > 1) { + thread = cpu_thread_in_core(cpu); + if (thread < 2) { + /* 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 */ + switch (weight) { + case 1: + /*divide by 1, do nothing*/ + break; + case 2: + smt_gain = smt_gain >> 1; + break; + case 4: + smt_gain = smt_gain >> 2; + break; + default: + smt_gain /= weight; + break; + } + + return smt_gain; + +} +#endif Index: linux-2.6.git/arch/powerpc/include/asm/cputable.h =================================================================== --- linux-2.6.git.orig/arch/powerpc/include/asm/cputable.h +++ linux-2.6.git/arch/powerpc/include/asm/cputable.h @@ -195,6 +195,7 @@ extern const char *powerpc_base_platform #define CPU_FTR_SAO LONG_ASM_CONST(0x0020000000000000) #define CPU_FTR_CP_USE_DCBTZ LONG_ASM_CONST(0x0040000000000000) #define CPU_FTR_UNALIGNED_LD_STD LONG_ASM_CONST(0x0080000000000000) +#define CPU_FTR_ASYNC_SMT4 LONG_ASM_CONST(0x0100000000000000) #ifndef __ASSEMBLY__ @@ -409,7 +410,7 @@ extern const char *powerpc_base_platform CPU_FTR_MMCRA | CPU_FTR_SMT | \ CPU_FTR_COHERENT_ICACHE | CPU_FTR_LOCKLESS_TLBIE | \ CPU_FTR_PURR | CPU_FTR_SPURR | CPU_FTR_REAL_LE | \ - CPU_FTR_DSCR | CPU_FTR_SAO) + CPU_FTR_DSCR | CPU_FTR_SAO | CPU_FTR_ASYNC_SMT4) #define CPU_FTRS_CELL (CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \ CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | \ CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \ -- 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/