Subject: Provide individual CPU usage measurement based on idle time
From: Carsten Emde <C.Emde@osadl.org>
Date: Sun, 22 Apr 2012 15:19:46 +0100
The various methods to determine CPU usage and load have a number of
disadvantages (see also Documentation/cpu-load.txt), and a
straight-forward method to gain usage information about a particular CPU
is lacking. However, in the context of setting CPU affinity and
isolation, it is often required to monitor the effective usage ratio of
a CPU.
This patch adds an additional CPU usage measuring method that is based
on idle time processing. The data are available for every CPU in
/proc/idleruntime/cpuN/data in the format "<idletime> <runtime>". The
counters can be reset by writing to /proc/idleruntime/resetall for all
CPUs and to /proc/idleruntime/cpuN/reset for a particular CPU,
respectively.
To calculate the CPU usage since the most recent reset, divide the
runtime by the sum of runtime plus idletime, e.g.
# for i in `ls -1d /proc/idleruntime/cpu* | sort -nk1.18`
> do
> echo "$i: `awk '{ print (100.0*$2) / ($1+$2)"%" }' <$i/data`"
> echo 1 >$i/reset
> done
/proc/idleruntime/cpu0: 72.0048%
/proc/idleruntime/cpu1: 5.49522%
/proc/idleruntime/cpu2: 0.27916%
/proc/idleruntime/cpu3: 32.3493%
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
---
init/Kconfig | 12 +++
kernel/sched/Makefile | 1
kernel/sched/core.c | 23 ++++++
kernel/sched/cpu_idleruntime.c | 136 +++++++++++++++++++++++++++++++++++++++++
kernel/sched/sched.h | 8 ++
5 files changed, 180 insertions(+)
Index: linux-3.12.13-rt21-fulldebug/init/Kconfig
===================================================================
--- linux-3.12.13-rt21-fulldebug.orig/init/Kconfig
+++ linux-3.12.13-rt21-fulldebug/init/Kconfig
@@ -407,6 +407,18 @@ config BSD_PROCESS_ACCT_V3
for processing it. A preliminary version of these tools is available
at <http://www.gnu.org/software/acct/>.
+config CPU_IDLERUNTIME
+ bool "Provide individual CPU usage measurement based on idle processing"
+ help
+ If you say Y here, individual CPU usage data will be provided that are
+ based on idle processing. The data are available for every CPU in
+ /proc/idleruntime/cpuN/data in the format "<idletime> <runtime>". The
+ counters can be reset by writing to /proc/idleruntime/resetall for all
+ CPUs and to /proc/idleruntime/cpuN/reset for a particular CPU,
+ respectively. To calculate the usage since the most recent reset,
+ the runtime must be devided by the sum of idletime plus runtime, e.g.
+ cat /proc/idleruntime/cpu0/data | awk '{print (100.0*$2) / ($1+$2)"%"}'
+
config TASKSTATS
bool "Export task/process statistics through netlink"
depends on NET
Index: linux-3.12.13-rt21-fulldebug/kernel/sched/Makefile
===================================================================
--- linux-3.12.13-rt21-fulldebug.orig/kernel/sched/Makefile
+++ linux-3.12.13-rt21-fulldebug/kernel/sched/Makefile
@@ -15,5 +15,6 @@ obj-y += core.o proc.o clock.o cputime.o
obj-$(CONFIG_SMP) += cpupri.o
obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
obj-$(CONFIG_SCHEDSTATS) += stats.o
+obj-$(CONFIG_CPU_IDLERUNTIME) += cpu_idleruntime.o
obj-$(CONFIG_SCHED_DEBUG) += debug.o
obj-$(CONFIG_CGROUP_CPUACCT) += cpuacct.o
Index: linux-3.12.13-rt21-fulldebug/kernel/sched/core.c
===================================================================
--- linux-3.12.13-rt21-fulldebug.orig/kernel/sched/core.c
+++ linux-3.12.13-rt21-fulldebug/kernel/sched/core.c
@@ -1903,6 +1903,37 @@ prepare_task_switch(struct rq *rq, struc
fire_sched_out_preempt_notifiers(prev, next);
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
+#ifdef CONFIG_CPU_IDLERUNTIME
+ if (is_idle_task(next)) {
+ int cpu = raw_smp_processor_id();
+
+ if (per_cpu(idlestop, cpu)) {
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&per_cpu(idleruntime_lock, cpu),
+ flags);
+ per_cpu(idlestart, cpu) = cpu_clock(cpu);
+ per_cpu(runtime, cpu) +=
+ per_cpu(idlestart, cpu) - per_cpu(idlestop, cpu);
+ raw_spin_unlock_irqrestore(&per_cpu(idleruntime_lock,
+ cpu), flags);
+ }
+ } else if (is_idle_task(prev)) {
+ int cpu = raw_smp_processor_id();
+
+ if (per_cpu(idlestart, cpu)) {
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&per_cpu(idleruntime_lock, cpu),
+ flags);
+ per_cpu(idlestop, cpu) = cpu_clock(cpu);
+ per_cpu(idletime, cpu) +=
+ per_cpu(idlestop, cpu) - per_cpu(idlestart, cpu);
+ raw_spin_unlock_irqrestore(&per_cpu(idleruntime_lock,
+ cpu), flags);
+ }
+ }
+#endif
}
/**
Index: linux-3.12.13-rt21-fulldebug/kernel/sched/cpu_idleruntime.c
===================================================================
--- /dev/null
+++ linux-3.12.13-rt21-fulldebug/kernel/sched/cpu_idleruntime.c
@@ -0,0 +1,138 @@
+/*
+ cpu_idleruntime.c: provide CPU usage data based on idle processing
+
+ Copyright (C) 2012 Carsten Emde <C.Emde@osadl.org>
+
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License
+ as published by the Free Software Foundation; either version 2
+ of the License, or (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+
+#include "sched.h"
+
+DEFINE_PER_CPU(unsigned long long, idlestart);
+DEFINE_PER_CPU(unsigned long long, idlestop);
+DEFINE_PER_CPU(unsigned long long, idletime);
+DEFINE_PER_CPU(unsigned long long, runtime);
+DEFINE_PER_CPU(raw_spinlock_t, idleruntime_lock);
+
+static int idleruntime_show(struct seq_file *m, void *v)
+{
+ unsigned long cpu = (unsigned long) m->private;
+ unsigned long long now;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&per_cpu(idleruntime_lock, cpu), flags);
+
+ /* Update runtime counter */
+ now = cpu_clock(cpu);
+ per_cpu(runtime, cpu) += now - per_cpu(idlestop, cpu);
+ per_cpu(idlestop, cpu) = now;
+
+ seq_printf(m, "%llu %llu\n", per_cpu(idletime, cpu),
+ per_cpu(runtime, cpu));
+
+ raw_spin_unlock_irqrestore(&per_cpu(idleruntime_lock, cpu), flags);
+
+ return 0;
+}
+
+static inline void idleruntime_reset1(int cpu)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&per_cpu(idleruntime_lock, cpu), flags);
+ per_cpu(idletime, cpu) = per_cpu(runtime, cpu) = 0;
+ per_cpu(idlestop, cpu) = cpu_clock(cpu);
+ raw_spin_unlock_irqrestore(&per_cpu(idleruntime_lock, cpu), flags);
+}
+
+static ssize_t idleruntime_reset(struct file *file, const char __user *buffer,
+ size_t len, loff_t *offset)
+{
+ unsigned long cpu = (unsigned long) PDE_DATA(file_inode(file));
+
+ idleruntime_reset1(cpu);
+ return len;
+}
+
+static ssize_t idleruntime_resetall(struct file *file,
+ const char __user *buffer,
+ size_t len, loff_t *offset)
+{
+ unsigned long cpu;
+
+ for_each_online_cpu(cpu)
+ idleruntime_reset1(cpu);
+ return len;
+}
+
+static const struct file_operations idleruntime_resetall_fops = {
+ .write = idleruntime_resetall,
+ .release = single_release,
+};
+
+static int idleruntime_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, idleruntime_show, PDE_DATA(inode));
+}
+
+static const struct file_operations idleruntime_fops = {
+ .open = idleruntime_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .write = idleruntime_reset,
+ .release = single_release,
+};
+
+static int __init proc_idleruntime_init(void)
+{
+ unsigned long cpu;
+ struct proc_dir_entry *root_idleruntime_dir;
+
+ root_idleruntime_dir = proc_mkdir("idleruntime", NULL);
+ if (!root_idleruntime_dir)
+ return 0;
+
+ if (!proc_create("resetall", S_IWUGO, root_idleruntime_dir,
+ &idleruntime_resetall_fops))
+ return 0;
+
+ for_each_possible_cpu(cpu) {
+ char name[32];
+ struct proc_dir_entry *idleruntime_cpudir;
+
+ raw_spin_lock_init(&per_cpu(idleruntime_lock, cpu));
+
+ snprintf(name, sizeof(name), "cpu%lu", cpu);
+ idleruntime_cpudir = proc_mkdir(name, root_idleruntime_dir);
+ if (!idleruntime_cpudir)
+ return 0;
+
+ if (!proc_create_data("data", S_IRUGO, idleruntime_cpudir,
+ &idleruntime_fops, (void *) cpu))
+ return 0;
+
+ if (!proc_create_data("reset", S_IWUGO, idleruntime_cpudir,
+ &idleruntime_fops, (void *) cpu)) {
+ remove_proc_entry("data", idleruntime_cpudir);
+ return 0;
+ }
+ }
+ return 0;
+}
+
+module_init(proc_idleruntime_init);
Index: linux-3.12.13-rt21-fulldebug/kernel/sched/sched.h
===================================================================
--- linux-3.12.13-rt21-fulldebug.orig/kernel/sched/sched.h
+++ linux-3.12.13-rt21-fulldebug/kernel/sched/sched.h
@@ -552,6 +552,14 @@ static inline u64 rq_clock_task(struct r
return rq->clock_task;
}
+#ifdef CONFIG_CPU_IDLERUNTIME
+extern DEFINE_PER_CPU(unsigned long long, idlestart);
+extern DEFINE_PER_CPU(unsigned long long, idlestop);
+extern DEFINE_PER_CPU(unsigned long long, idletime);
+extern DEFINE_PER_CPU(unsigned long long, runtime);
+extern DEFINE_PER_CPU(raw_spinlock_t, idleruntime_lock);
+#endif
+
#ifdef CONFIG_SMP
#define rcu_dereference_check_sched_domain(p) \