Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754655AbbGaXVX (ORCPT ); Fri, 31 Jul 2015 19:21:23 -0400 Received: from mga02.intel.com ([134.134.136.20]:7710 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754609AbbGaXVW (ORCPT ); Fri, 31 Jul 2015 19:21:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,587,1432623600"; d="scan'208";a="617072748" Date: Fri, 31 Jul 2015 16:21:19 -0700 (PDT) From: Vikas Shivappa X-X-Sender: vikas@vshiva-Udesk To: Peter Zijlstra cc: Vikas Shivappa , linux-kernel@vger.kernel.org, vikas.shivappa@intel.com, x86@kernel.org, hpa@zytor.com, tglx@linutronix.de, mingo@kernel.org, tj@kernel.org, Matt Fleming , "Auld, Will" , "Williamson, Glenn P" , "Juvva, Kanaka D" Subject: Re: [PATCH 8/9] x86/intel_rdt: Hot cpu support for Cache Allocation In-Reply-To: <20150729155302.GX25159@twins.programming.kicks-ass.net> Message-ID: References: <1435789270-27010-1-git-send-email-vikas.shivappa@linux.intel.com> <1435789270-27010-9-git-send-email-vikas.shivappa@linux.intel.com> <20150729155302.GX25159@twins.programming.kicks-ass.net> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2227 Lines: 74 On Wed, 29 Jul 2015, Peter Zijlstra wrote: > On Wed, Jul 01, 2015 at 03:21:09PM -0700, Vikas Shivappa wrote: >> +/* >> + * cbm_update_msrs() - Updates all the existing IA32_L3_MASK_n MSRs >> + * which are one per CLOSid except IA32_L3_MASK_0 on the current package. >> + */ >> +static void cbm_update_msrs(void *info) >> +{ >> + int maxid = boot_cpu_data.x86_cache_max_closid; >> + unsigned int i; >> + >> + /* >> + * At cpureset, all bits of IA32_L3_MASK_n are set. >> + * The index starts from one as there is no need >> + * to update IA32_L3_MASK_0 as it belongs to root cgroup >> + * whose cache mask is all 1s always. >> + */ >> + for (i = 1; i < maxid; i++) { >> + if (ccmap[i].clos_refcnt) >> + cbm_cpu_update((void *)i); >> + } >> +} >> + >> +static inline void intel_rdt_cpu_start(int cpu) >> +{ >> + struct intel_pqr_state *state = &per_cpu(pqr_state, cpu); >> + >> + state->closid = 0; >> + mutex_lock(&rdt_group_mutex); >> + if (rdt_cpumask_update(cpu)) >> + smp_call_function_single(cpu, cbm_update_msrs, NULL, 1); >> + mutex_unlock(&rdt_group_mutex); >> +} > > If you were to guard your array with both a mutex and a raw_spinlock > then you can avoid the IPI and use CPU_STARTING. Cpu_online was just good enough as the tasks would be ready to be scheduled. iow , its just at the right time. could avoid using the interrupt disabled time ? Dont really need the *interrupt disabled* cpu_starting notification - can leave that for more important code/lock free code can go there. or this change should not be a big concern ? > >> +static int intel_rdt_cpu_notifier(struct notifier_block *nb, >> + unsigned long action, void *hcpu) >> +{ >> + unsigned int cpu = (unsigned long)hcpu; >> + >> + switch (action) { >> + case CPU_DOWN_FAILED: >> + case CPU_ONLINE: >> + intel_rdt_cpu_start(cpu); >> + break; >> + case CPU_DOWN_PREPARE: >> + intel_rdt_cpu_exit(cpu); >> + break; >> + default: >> + break; >> + } >> + >> + return NOTIFY_OK; >> } > -- 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/