From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gautham R Shenoy Subject: Re: [RFC PATCH] PM/CPU: Parallel enabling nonboot cpus with resume devices Date: Fri, 8 Aug 2014 16:25:02 +0530 Message-ID: <20140808105501.GA15048@in.ibm.com> References: <1406106694-3306-1-git-send-email-tianyu.lan@intel.com> Reply-To: ego@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e9.ny.us.ibm.com ([32.97.182.139]:32778 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755216AbaHHKzv (ORCPT ); Fri, 8 Aug 2014 06:55:51 -0400 Received: from /spool/local by e9.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 8 Aug 2014 06:55:50 -0400 Content-Disposition: inline In-Reply-To: <1406106694-3306-1-git-send-email-tianyu.lan@intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Lan Tianyu Cc: rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz, peterz@infradead.org, toshi.kani@hp.com, mingo@kernel.org, akpm@linux-foundation.org, todd.e.brandt@linux.intel.com, fabf@skynet.be, srivatsa.bhat@linux.vnet.ibm.com, ego@linux.vnet.ibm.com, rafael.j.wysocki@intel.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Hi Lan, On Wed, Jul 23, 2014 at 05:11:34PM +0800, Lan Tianyu wrote: > In the current world, all nonboot cpus are enabled serially during system > resume. System resume sequence is that boot cpu enables nonboot cpu one by > one and then resume devices. Before resuming devices, there are few tasks > assigned to nonboot cpus after they are brought up. This waste cpu usage. > > To accelerate S3, this patches adds a new kernel configure > PM_PARALLEL_CPU_UP_FOR_SUSPEND to allow boot cpu to go forward to resume > devices after bringing up one nonboot cpu. The nonboot cpu will be in charge > of bringing up other cpus. This makes enabling cpu2~x parallel with resuming > devices. From the test result on 4 logical core laptop, the time of resume > device almost wasn't affected by enabling nonboot cpus lately while the start > point is almost 30ms earlier than before. > > Signed-off-by: Lan Tianyu > --- > kernel/cpu.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++------ > kernel/power/Kconfig | 13 +++++++++ > 2 files changed, 86 insertions(+), 9 deletions(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index a343bde..d4c1353 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -551,9 +551,27 @@ void __weak arch_enable_nonboot_cpus_end(void) > { > } > > +static int _cpu_up_with_trace(int cpu) > +{ > + int error; > + > + trace_suspend_resume(TPS("CPU_ON"), cpu, true); > + error = _cpu_up(cpu, 1); > + trace_suspend_resume(TPS("CPU_ON"), cpu, false); > + if (error) { > + pr_warn("Error taking CPU%d up: %d\n", cpu, error); > + return error; > + } > + > + pr_info("CPU%d is up\n", cpu); > + return 0; > +} > + [..snip..] > > + > +void __ref enable_nonboot_cpus(void) > +{ > + struct task_struct *tsk; > + int cpu; > + > + /* Allow everyone to use the CPU hotplug again */ > + cpu_maps_update_begin(); > + cpu_hotplug_disabled = 0; > + if (cpumask_empty(frozen_cpus)) > + goto out; > + > + arch_enable_nonboot_cpus_begin(); > + > + cpu = cpumask_first(frozen_cpus); > + cpumask_clear_cpu(cpu, frozen_cpus); > + > + _cpu_up_with_trace(cpu); We should be handling the error returned by _cpu_up_with_trace() in case 'cpu' fails to come online. Unless it is something that I am not aware of it doesn't make much sense to create a kthread on a cpu that we know has failed to come online. > + > + if (cpumask_empty(frozen_cpus)) { > + arch_enable_nonboot_cpus_end(); > + } else { > + tsk = kthread_create_on_cpu(async_enable_nonboot_cpus, > + NULL, cpu, "async-enable-nonboot-cpus"); > + if (IS_ERR(tsk)) { > + pr_err("Failed to create async enable nonboot cpus thread.\n"); > + goto out; > + } > + > + kthread_unpark(tsk); > + } > +out: > + cpu_maps_update_done(); > +} > +#endif > + -- Thanks and Regards gautham.