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Commit 6570a9a1 authored by Rik van Riel's avatar Rik van Riel Committed by Greg Kroah-Hartman
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show nohz_full cpus in sysfs 



Currently there is no way to query which CPUs are in nohz_full
mode from userspace.

Export the CPU list running in nohz_full mode in sysfs,
specifically in the file /sys/devices/system/cpu/nohz_full

This can be used by system management tools like libvirt,
openstack, and others to ensure proper task placement.

Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarMike Galbraith <umgwanakikbuti@gmail.com>
Acked-by: default avatarChris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 59f30abe

drivers/base/cpu.c

+17 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/acpi.h>

#include <linux/of.h>

#include <linux/cpufeature.h>

#include <linux/tick.h>



#include "base.h"
@@ -276,6 +277,19 @@ static ssize_t print_cpus_isolated(struct device *dev, 
}

static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);



#ifdef CONFIG_NO_HZ_FULL

static ssize_t print_cpus_nohz_full(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(tick_nohz_full_mask));



	return n;

}

static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);

#endif



static void cpu_device_release(struct device *dev)

{

	/*
@@ -443,6 +457,9 @@ static struct attribute *cpu_root_attrs[] = { 
	&dev_attr_kernel_max.attr,

	&dev_attr_offline.attr,

	&dev_attr_isolated.attr,

#ifdef CONFIG_NO_HZ_FULL

	&dev_attr_nohz_full.attr,

#endif

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE

	&dev_attr_modalias.attr,

#endif