Subject: Provide individual CPU usage measurement based on idle time
From: Carsten Emde <C.Emde@osadl.org>
Date: Fri, 4 Sep 2015 20:41:40 +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/cpuN/reset.
To calculate the per-core 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 -nk1.22`
> 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%
In addition, summed up data of all present CPUs are available in
/proc/idleruntime/all in the same format as above. Thus, to calculate
the overall CPU usage since the most recent reset, the following command
may be used:
awk '{ print (100.0*$2) / ($1+$2)"%" }' </proc/idleruntime/all/data
To reset the counters althogether write to /proc/idleruntime/all/reset.
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
---
init/Kconfig | 28 +++++
kernel/sched/Makefile | 2
kernel/sched/core.c | 31 +++++
kernel/sched/cpu_idleruntime.c | 226 +++++++++++++++++++++++++++++++++++++++++
kernel/sched/sched.h | 8 +
5 files changed, 295 insertions(+)
Index: linux-6.1.38-rt12/init/Kconfig
===================================================================
@ linux-6.1.38-rt12/init/Kconfig:584 @ 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 and for
+ all present CPUs summed up in /proc/idleruntime/cpuN/data and
+ /proc/idleruntime/all/data, respectively, in the format
+ "<idletime> <runtime>". The counters can be reset by writing to
+ /proc/idleruntime/cpuN/reset separately for every CPU and to
+ /proc/idleruntime/all/reset for all present CPUs at once. To calculate
+ the CPU usage since the most recent reset, the runtime must be devided
+ by the sum of idletime plus runtime
+ awk '{print (100.0*$2) / ($1+$2)"%"}' </proc/idleruntime/cpu0/data
+ for every CPU or
+ awk '{print (100.0*$2) / ($1+$2)"%"}' </proc/idleruntime/all/data
+ for all CPUs altogether. The shell code snippet
+ # for i in `ls -1d /proc/idleruntime/cpu* | sort -nk1.22`
+ > do
+ > echo "$i: `awk '{ print (100.0*$2) / ($1+$2)"%" }' <$i/data`"
+ > echo 1 >$i/reset
+ > done
+ may produce
+ /proc/idleruntime/cpu0: 72.0048%
+ /proc/idleruntime/cpu1: 5.49522%
+ /proc/idleruntime/cpu2: 0.27916%
+ /proc/idleruntime/cpu3: 32.3493%
+ on a four-core processor.
+
config TASKSTATS
bool "Export task/process statistics through netlink"
depends on NET
Index: linux-6.1.38-rt12/kernel/sched/Makefile
===================================================================
--- linux-6.1.38-rt12.orig/kernel/sched/Makefile
+++ linux-6.1.38-rt12/kernel/sched/Makefile
@ linux-6.1.38-rt12/init/Kconfig:35 @ obj-y += core.o
obj-y += fair.o
obj-y += build_policy.o
obj-y += build_utility.o
+obj-y += cpu_idleruntime.o
+
Index: linux-6.1.38-rt12/kernel/sched/core.c
===================================================================
--- linux-6.1.38-rt12.orig/kernel/sched/core.c
+++ linux-6.1.38-rt12/kernel/sched/core.c
@ linux-6.1.38-rt12/init/Kconfig:5172 @ prepare_task_switch(struct rq *rq, struc
kmap_local_sched_out();
prepare_task(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-6.1.38-rt12/kernel/sched/cpu_idleruntime.c
===================================================================
--- /dev/null
+++ linux-6.1.38-rt12/kernel/sched/cpu_idleruntime.c
@ linux-6.1.38-rt12/init/Kconfig:4 @
+/*
+ cpu_idleruntime.c: provide CPU usage data based on idle processing
+
+ Copyright (C) 2012,2015 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 <linux/cpu.h>
+#include <linux/sched/clock.h>
+#include <linux/sched/cputime.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 DEFINE_PER_CPU(struct proc_dir_entry *, idleruntime_dir);
+static struct proc_dir_entry *root_idleruntime_dir;
+
+static void idleruntime_get(unsigned long cpu, unsigned long long *cpuidletime,
+ unsigned long long *cpuruntime)
+{
+ unsigned long long now;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&per_cpu(idleruntime_lock, cpu), flags);
+
+ /* Update runtime counter */
+ now = cpu_clock(cpu);
+ if (is_idle_task(cpu_rq(cpu)->curr))
+ per_cpu(idletime, cpu) += now - per_cpu(idlestart, cpu);
+ else
+ per_cpu(runtime, cpu) += now - per_cpu(idlestop, cpu);
+
+ *cpuidletime = per_cpu(idletime, cpu);
+ *cpuruntime = per_cpu(runtime, cpu);
+
+ raw_spin_unlock_irqrestore(&per_cpu(idleruntime_lock, cpu), flags);
+
+}
+
+static void idleruntime_output(struct seq_file *m, unsigned long long idletime,
+ unsigned long long runtime)
+{
+ seq_printf(m, "%llu %llu\n", idletime, runtime);
+}
+
+static int idleruntime_show(struct seq_file *m, void *v)
+{
+ unsigned long cpu = (unsigned long) m->private;
+ unsigned long long cpuidletime, cpuruntime;
+
+ idleruntime_get(cpu, &cpuidletime, &cpuruntime);
+ idleruntime_output(m, cpuidletime, cpuruntime);
+
+ return 0;
+}
+
+static int idleruntime_show_all(struct seq_file *m, void *v)
+{
+ unsigned long cpu;
+ unsigned long long total_idletime = 0ULL, total_runtime = 0ULL;
+
+ preempt_disable();
+
+ for_each_present_cpu(cpu) {
+ unsigned long long cpuidletime, cpuruntime;
+
+ idleruntime_get(cpu, &cpuidletime, &cpuruntime);
+ total_idletime += cpuidletime;
+ total_runtime += cpuruntime;
+ }
+
+ preempt_enable();
+
+ idleruntime_output(m, total_idletime, total_runtime);
+
+ return 0;
+}
+
+static inline void idleruntime_reset1(unsigned long 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(idlestart, cpu) = 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_reset_all(struct file *file,
+ const char __user *buffer,
+ size_t len, loff_t *offset)
+{
+ unsigned long cpu;
+
+ preempt_disable();
+
+ for_each_present_cpu(cpu)
+ idleruntime_reset1(cpu);
+
+ preempt_enable();
+
+ return len;
+}
+
+static int idleruntime_open_all(struct inode *inode, struct file *file)
+{
+ return single_open(file, idleruntime_show_all, pde_data(inode));
+}
+
+static const struct proc_ops idleruntime_all_proc_ops = {
+ .proc_open = idleruntime_open_all,
+ .proc_read = seq_read,
+ .proc_lseek = seq_lseek,
+ .proc_write = idleruntime_reset_all,
+ .proc_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 proc_ops idleruntime_proc_ops = {
+ .proc_open = idleruntime_open,
+ .proc_read = seq_read,
+ .proc_lseek = seq_lseek,
+ .proc_write = idleruntime_reset,
+ .proc_release = single_release,
+};
+
+static int setup_procfiles(unsigned int cpu)
+{
+ char name[32];
+ struct proc_dir_entry *idleruntime_cpudir = NULL;
+
+ if (root_idleruntime_dir) {
+ snprintf(name, sizeof(name), "cpu%d", cpu);
+ idleruntime_cpudir = proc_mkdir(name, root_idleruntime_dir);
+ }
+
+ if (idleruntime_cpudir) {
+ proc_create_data("data", S_IRUGO, idleruntime_cpudir,
+ &idleruntime_proc_ops, (void *) (long) cpu);
+ proc_create_data("reset", S_IWUGO, idleruntime_cpudir,
+ &idleruntime_proc_ops, (void *) (long) cpu);
+ }
+ per_cpu(idleruntime_dir, cpu) = idleruntime_cpudir;
+
+ return 0;
+}
+
+static int unset_procfiles(unsigned int cpu)
+{
+ struct proc_dir_entry *idleruntime_cpudir =
+ per_cpu(idleruntime_dir, cpu);
+
+ if (idleruntime_cpudir) {
+ remove_proc_entry("reset", idleruntime_cpudir);
+ remove_proc_entry("data", idleruntime_cpudir);
+ proc_remove(idleruntime_cpudir);
+ per_cpu(idleruntime_dir, cpu) = NULL;
+ }
+
+ return 0;
+}
+
+static int __init idleruntime_init(void)
+{
+ root_idleruntime_dir = proc_mkdir("idleruntime", NULL);
+ if (root_idleruntime_dir) {
+ struct proc_dir_entry *idleruntime_alldir;
+ unsigned long cpu, cpus = 0;
+
+ for_each_possible_cpu(cpu) {
+ per_cpu(idlestart, cpu) = per_cpu(idlestop, cpu) =
+ cpu_clock(cpu);
+ raw_spin_lock_init(&per_cpu(idleruntime_lock, cpu));
+ cpus++;
+ }
+
+ if (cpus > 1) {
+ idleruntime_alldir = proc_mkdir("all",
+ root_idleruntime_dir);
+ proc_create_data("data", S_IRUGO, idleruntime_alldir,
+ &idleruntime_all_proc_ops, NULL);
+ proc_create_data("reset", S_IWUGO, idleruntime_alldir,
+ &idleruntime_all_proc_ops, NULL);
+ }
+
+ cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+ "idleruntime:online",
+ setup_procfiles,
+ unset_procfiles);
+ }
+ return 0;
+}
+
+early_initcall(idleruntime_init);
Index: linux-6.1.38-rt12/kernel/sched/sched.h
===================================================================
--- linux-6.1.38-rt12.orig/kernel/sched/sched.h
+++ linux-6.1.38-rt12/kernel/sched/sched.h
@ linux-6.1.38-rt12/init/Kconfig:1685 @ this_rq_lock_irq(struct rq_flags *rf)
return rq;
}
+#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_NUMA
enum numa_topology_type {
NUMA_DIRECT,