linux-kernel - Re: [PATCH 1/2] show isolated cpus in sysfs

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Message-ID: <20150424211120.GA26965@lerouge>
Date:	Fri, 24 Apr 2015 23:11:29 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	riel@...hat.com, Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, tj@...nel.org,
	umgwanakikbuti@...il.com, lizefan@...wei.com,
	gregkh@...uxfoundation.org
Subject: Re: [PATCH 1/2] show isolated cpus in sysfs

On Fri, Apr 24, 2015 at 03:24:27PM -0400, riel@...hat.com wrote:
> From: Rik van Riel <riel@...hat.com>
> 
> After system bootup, there is no totally reliable way to see
> which CPUs are isolated, because the kernel may modify the
> CPUs specified on the isolcpus= kernel command line option.
> 
> Export the CPU list that actually got isolated in sysfs,
> specifically in the file /sys/devices/system/cpu/isolated
> 
> This can be used by system management tools like libvirt,
> openstack, and others to ensure proper placement of tasks.
> 
> Suggested-by: Li Zefan <lizefan@...wei.com>
> Signed-off-by: Rik van Riel <riel@...hat.com>

This patch should go through Peterz.

> ---
>  drivers/base/cpu.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index f160ea44a86d..ea23ee7b545b 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -265,6 +265,17 @@ static ssize_t print_cpus_offline(struct device *dev,
>  }
>  static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
>  
> +static ssize_t print_cpus_isolated(struct device *dev,
> +				  struct device_attribute *attr, char *buf)
> +{
> +	int n = 0, len = PAGE_SIZE-2;
> +
> +	n = scnprintf(buf, len, "%*pbl\n", cpumask_pr_args(cpu_isolated_map));
> +
> +	return n;
> +}
> +static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);
> +
>  static void cpu_device_release(struct device *dev)
>  {
>  	/*
> @@ -431,6 +442,7 @@ static struct attribute *cpu_root_attrs[] = {
>  	&cpu_attrs[2].attr.attr,
>  	&dev_attr_kernel_max.attr,
>  	&dev_attr_offline.attr,
> +	&dev_attr_isolated.attr,
>  #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
>  	&dev_attr_modalias.attr,
>  #endif
> -- 
> 2.1.0
> 
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