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Date: Mon, 5 Apr 2010 21:14:06 -0700
From: Mike Chan <mike@...roid.com>
To: balbir@...ux.vnet.ibm.com
Cc: menage@...gle.com, cpufreq@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] sched: cpuacct: Track cpuusage per cpu frequency
On Mon, Apr 5, 2010 at 7:13 PM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> * Mike Chan <mike@...roid.com> [2010-04-05 12:33:24]:
>
>> New file: cpuacct.cpufreq when CONFIG_CPU_FREQ_STATS is enabled.
>>
>> cpuacct.cpufreq accounts for cpu time per-cpu frequency, time is exported
>> in nano-seconds
>>
>> We do not know the cpufreq table size at compile time.
>> So a new config option CONFIG_CPUACCT_CPUFREQ_TABLE_MAX is intruduced,
>> to determine the cpufreq table per-cpu in the cpuacct struct.
>>
>> Signed-off-by: Mike Chan <mike@...roid.com>
>> ---
>> init/Kconfig | 5 +++
>> kernel/sched.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 104 insertions(+), 0 deletions(-)
>>
>> diff --git a/init/Kconfig b/init/Kconfig
>> index eb77e8c..e1e86df 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -534,6 +534,11 @@ config CGROUP_CPUACCT
>> Provides a simple Resource Controller for monitoring the
>> total CPU consumed by the tasks in a cgroup.
>>
>> +config CPUACCT_CPUFREQ_TABLE_MAX
>> + int "Max CPUFREQ table size"
>> + depends on CGROUP_CPUACCT && CPU_FREQ_TABLE
>> + default 32
>> +
>> config RESOURCE_COUNTERS
>> bool "Resource counters"
>> help
>> diff --git a/kernel/sched.c b/kernel/sched.c
>> index 528a105..a0b56b5 100644
>> --- a/kernel/sched.c
>> +++ b/kernel/sched.c
>> @@ -71,6 +71,7 @@
>> #include <linux/debugfs.h>
>> #include <linux/ctype.h>
>> #include <linux/ftrace.h>
>> +#include <linux/cpufreq.h>
>>
>> #include <asm/tlb.h>
>> #include <asm/irq_regs.h>
>> @@ -8817,6 +8818,11 @@ struct cgroup_subsys cpu_cgroup_subsys = {
>> * (balbir@...ibm.com).
>> */
>>
>> +#ifdef CONFIG_CPU_FREQ_STAT
>> +/* The alloc_percpu macro uses typeof so we must define a type here. */
>> +typedef struct { u64 usage[CONFIG_CPUACCT_CPUFREQ_TABLE_MAX]; } cpufreq_usage_t;
>> +#endif
>> +
>> /* track cpu usage of a group of tasks and its child groups */
>> struct cpuacct {
>> struct cgroup_subsys_state css;
>> @@ -8824,6 +8830,10 @@ struct cpuacct {
>> u64 __percpu *cpuusage;
>> struct percpu_counter cpustat[CPUACCT_STAT_NSTATS];
>> struct cpuacct *parent;
>> +#ifdef CONFIG_CPU_FREQ_STAT
>> + /* cpufreq_usage is a pointer to an array of u64-types on every cpu */
>> + cpufreq_usage_t *cpufreq_usage;
>> +#endif
>> };
>>
>> struct cgroup_subsys cpuacct_subsys;
>> @@ -8856,6 +8866,10 @@ static struct cgroup_subsys_state *cpuacct_create(
>> if (!ca->cpuusage)
>> goto out_free_ca;
>>
>> +#ifdef CONFIG_CPU_FREQ_STAT
>> + ca->cpufreq_usage = alloc_percpu(cpufreq_usage_t);
>> +#endif
>> +
>> for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
>> if (percpu_counter_init(&ca->cpustat[i], 0))
>> goto out_free_counters;
>> @@ -8888,6 +8902,74 @@ cpuacct_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
>> kfree(ca);
>> }
>>
>> +#ifdef CONFIG_CPU_FREQ_STAT
>> +static int cpufreq_index;
>> +static int cpuacct_cpufreq_notify(struct notifier_block *nb, unsigned long val,
>> + void *data)
>> +{
>> + int ret;
>> + struct cpufreq_policy *policy;
>> + struct cpufreq_freqs *freq = data;
>> + struct cpufreq_frequency_table *table;
>> +
>> + if (val != CPUFREQ_POSTCHANGE)
>> + return 0;
>> +
>> + /* Update cpufreq_index with current speed */
>> + table = cpufreq_frequency_get_table(freq->cpu);
>> + policy = cpufreq_cpu_get(freq->cpu);
>> + ret = cpufreq_frequency_table_target(policy, table,
>> + cpufreq_quick_get(freq->cpu),
>
> Since you've already done a cpufreq_cpu_get, can't you directly
> dereference policy->cur here?
Yes, we could. I thought I would use the cpufreq public api's from the
header just incase there were any core-internal changes in the future.
Although its probably safe to use policy->cur.
>
>> + CPUFREQ_RELATION_L, &cpufreq_index);
>
> The code is unclear
>
I can put a comment here about this. Basically when selecting a
frequency from the freq_table using the cpufreq, incase the exact
frequency you are looking for does not exist in the table you can
specify "highest speed at or below requested speed" or "lowest speed
at or below requested speed", either of these params work here since
the speed we are choosing will always exist in the freq_table.
>> + cpufreq_cpu_put(policy);
>> + return ret;
>> +}
>> +
>> +static struct notifier_block cpufreq_notifier = {
>> + .notifier_call = cpuacct_cpufreq_notify,
>> +};
>> +
>> +static __init int cpuacct_init(void)
>> +{
>> + return cpufreq_register_notifier(&cpufreq_notifier,
>> + CPUFREQ_TRANSITION_NOTIFIER);
>> +}
>> +
>> +module_init(cpuacct_init);
>> +
>> +static int cpuacct_cpufreq_show(struct cgroup *cgrp, struct cftype *cft,
>> + struct cgroup_map_cb *cb)
>> +{
>> + int i;
>> + unsigned int cpu;
>> + char buf[32];
>> + struct cpuacct *ca = cgroup_ca(cgrp);
>> + struct cpufreq_frequency_table *table =
>> + cpufreq_frequency_get_table(smp_processor_id());
>> +
>> + for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
>> + u64 total = 0;
>> +
>> + if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>> + continue;
>> +
>> + for_each_present_cpu(cpu) {
>
> Why do we care about all present cpus? A comment would be nice, is
> this an ABI thing? Do we care about data of offline cpus, etc.
If we have a system with cpu hotplug and cpu's come online and offline
for the lifetime of the system, we want to include their statistics
when you dump the file.
If you only care about currently online, you can have a case where
Chrome has been running on CPU1, and you hotplug CPU1, immediately
after you read cpuacct.cpufreq. I can add a comment here.
>
>> + cpufreq_usage_t *cpufreq_usage;
>> +
>> + cpufreq_usage = per_cpu_ptr(ca->cpufreq_usage, cpu);
>> + table = cpufreq_frequency_get_table(cpu);
>> +
>> + total += cpufreq_usage->usage[i];
>> + }
>> +
>> + snprintf(buf, sizeof(buf), "%d", table[i].frequency);
>> + cb->fill(cb, buf, total);
>> + }
>> +
>> + return 0;
>> +}
>> +#endif
>> +
>> static u64 cpuacct_cpuusage_read(struct cpuacct *ca, int cpu)
>> {
>> u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
>> @@ -9003,6 +9085,12 @@ static struct cftype files[] = {
>> .name = "stat",
>> .read_map = cpuacct_stats_show,
>> },
>> +#ifdef CONFIG_CPU_FREQ_STAT
>> + {
>> + .name = "cpufreq",
>> + .read_map = cpuacct_cpufreq_show,
>> + },
>> +#endif
>> };
>>
>> static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
>> @@ -9031,6 +9119,17 @@ static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
>>
>> for (; ca; ca = ca->parent) {
>> u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
>> +#ifdef CONFIG_CPU_FREQ_STAT
>> + cpufreq_usage_t *cpufreq_usage =
>> + per_cpu_ptr(ca->cpufreq_usage, cpu);
>> +
>> + if (cpufreq_index > CONFIG_CPUACCT_CPUFREQ_TABLE_MAX)
>> + printk_once(KERN_WARNING "cpuacct_charge: "
>> + "cpufreq_index: %d exceeds max table "
>> + "size\n", cpufreq_index);
>
> WARN_ON_ONCE() would be more readable, IMHO
Although I do admit WARN is much easier to spot, WARN gives a
stacktrace, which isn't too useful in this case and wastes dmesg
buffer.
>
>> + else
>> + cpufreq_usage->usage[cpufreq_index] += cputime;
>> +#endif
>> *cpuusage += cputime;
>> }
>>
>> --
>> 1.7.0.1
>>
>
> --
> Three Cheers,
> Balbir
>
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