linux-kernel - Re: [RFC PATCH V2] PM/CPU: Parallel enalbing nonboot cpus with resume devices

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Date:	Fri, 29 Aug 2014 11:40:50 +0800
From:	Lan Tianyu <tianyu.lan@...el.com>
To:	peterz@...radead.org, mingo@...nel.org, rafael.j.wysocki@...el.com,
	srivatsa@....edu, akpm@...ux-foundation.org, laijs@...fujitsu.com,
	toshi.kani@...com, todd.e.brandt@...ux.intel.com,
	wangyun@...ux.vnet.ibm.com, ego@...ux.vnet.ibm.com, fabf@...net.be,
	linux@....linux.org.uk
CC:	oleg@...hat.com, srivatsa.bhat@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V2] PM/CPU: Parallel enalbing nonboot cpus with resume
 devices

On 2014年08月22日 16:33, 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 allows 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.
> 
> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>
> ---
> Change since V1:
> 	Remove PM_PARALLEL_CPU_UP_FOR_SUSPEND kernel config and make
> paralleling cpu as default behaviour. Add error handling for 
> failure of the first frozen cpu online.
> 
> So far, I just tested the patch on the Intel machines. It's better
> to test it on the others Arch platforms. Appreciate a lot if some
> one can help test it. 
> 

Hi All:
	Any comments on this patch?  Thanks.

>  kernel/cpu.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 58 insertions(+), 12 deletions(-)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index a343bde..9bc8497 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -551,8 +551,42 @@ 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;
> +}
> +
> +static int async_enable_nonboot_cpus(void *data)
> +{
> +	int cpu;
> +
> +	cpu_maps_update_begin();
> +	arch_enable_nonboot_cpus_begin();
> +
> +	for_each_cpu(cpu, frozen_cpus) {
> +		_cpu_up_with_trace(cpu);
> +	}
> +
> +	arch_enable_nonboot_cpus_end();
> +	cpumask_clear(frozen_cpus);
> +	cpu_maps_update_done();
> +	return 0;
> +}
> +
>  void __ref enable_nonboot_cpus(void)
>  {
> +	struct task_struct *tsk;
>  	int cpu, error;
>  
>  	/* Allow everyone to use the CPU hotplug again */
> @@ -563,22 +597,34 @@ void __ref enable_nonboot_cpus(void)
>  
>  	pr_info("Enabling non-boot CPUs ...\n");
>  
> -	arch_enable_nonboot_cpus_begin();
> +	cpu = cpumask_first(frozen_cpus);
> +	cpumask_clear_cpu(cpu, frozen_cpus);
>  
> -	for_each_cpu(cpu, frozen_cpus) {
> -		trace_suspend_resume(TPS("CPU_ON"), cpu, true);
> -		error = _cpu_up(cpu, 1);
> -		trace_suspend_resume(TPS("CPU_ON"), cpu, false);
> -		if (!error) {
> -			pr_info("CPU%d is up\n", cpu);
> -			continue;
> +	error = _cpu_up_with_trace(cpu);
> +	if (cpumask_empty(frozen_cpus))
> +		goto out;
> +
> +	if (error) {
> +		/*
> +		 * If fail to bring up the first frozen cpus,
> +		 * enable the rest frozen cpus on the boot cpu.
> +		 */
> +		arch_enable_nonboot_cpus_begin();
> +		for_each_cpu(cpu, frozen_cpus) {
> +			_cpu_up_with_trace(cpu);
>  		}
> -		pr_warn("Error taking CPU%d up: %d\n", cpu, error);
> -	}
> +		arch_enable_nonboot_cpus_end();
>  
> -	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;
> +		}
>  
> -	cpumask_clear(frozen_cpus);
> +		kthread_unpark(tsk);
> +	}
>  out:
>  	cpu_maps_update_done();
>  }
> 


-- 
Best regards
Tianyu Lan
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