[PATCH] idle cputime accounting

The cpu time spent by the idle process actually doing something is
currently accounted as idle time. This is plain wrong, the architectures
that support VIRT_CPU_ACCOUNTING=y can do better: distinguish between the
time spent doing nothing and the time spent by idle doing work. The first
is accounted with account_idle_time and the second with account_system_time.
The architectures that use the account_xxx_time interface directly and not
the account_xxx_ticks interface now need to do the check for the idle
process in their arch code. In particular to improve the system vs true
idle time accounting the arch code needs to measure the true idle time
instead of just testing for the idle process.
To improve the tick based accounting as well we would need an architecture
primitive that can tell us if the pt_regs of the interrupted context
points to the magic instruction that halts the cpu.

In addition idle time is no more added to the stime of the idle process.
This field now contains the system time of the idle process as it should
be. On systems without VIRT_CPU_ACCOUNTING this will always be zero as
every tick that occurs while idle is running will be accounted as idle
time.

This patch contains the necessary common code changes to be able to
distinguish idle system time and true idle time. The architectures with
support for VIRT_CPU_ACCOUNTING need some changes to exploit this.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 4ee367817049aba6fcc1572cdd57fe6258e82604..f0ebb342409d0b4ab3cd5d9ba470aa3284ef2667 100644 (file)
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -93,7 +93,10 @@ void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
        now = ia64_get_itc();
 
        delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
-       account_system_time(prev, 0, delta_stime, delta_stime);
+       if (idle_task(smp_processor_id()) != prev)
+               account_system_time(prev, 0, delta_stime, delta_stime);
+       else
+               account_idle_time(delta_stime);
 
        if (pi->ac_utime) {
                delta_utime = cycle_to_cputime(pi->ac_utime);
@@ -120,7 +123,10 @@ void account_system_vtime(struct task_struct *tsk)
        now = ia64_get_itc();
 
        delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
-       account_system_time(tsk, 0, delta_stime, delta_stime);
+       if (irq_count() || idle_task(smp_processor_id()) != tsk)
+               account_system_time(tsk, 0, delta_stime, delta_stime);
+       else
+               account_idle_time(delta_stime);
        ti->ac_stime = 0;
 
        ti->ac_stamp = now;

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 51b201ddf9a160002d10ff3c61cd9bb2e40119a5..fb7049c054c061765feae824d635da3477d1b624 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -33,6 +33,7 @@
 #include <linux/mqueue.h>
 #include <linux/hardirq.h>
 #include <linux/utsname.h>
+#include <linux/kernel_stat.h>
 
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 92650ccad2e1c215645a0e535e471e9f3e2958a0..3be355c1cfa73f8d6363ee9012f6e094f30652ae 100644 (file)
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -256,7 +256,10 @@ void account_system_vtime(struct task_struct *tsk)
                delta += sys_time;
                get_paca()->system_time = 0;
        }
-       account_system_time(tsk, 0, delta, deltascaled);
+       if (in_irq() || idle_task(smp_processor_id()) != tsk)
+               account_system_time(tsk, 0, delta, deltascaled);
+       else
+               account_idle_time(delta);
        per_cpu(cputime_last_delta, smp_processor_id()) = delta;
        per_cpu(cputime_scaled_last_delta, smp_processor_id()) = deltascaled;
        local_irq_restore(flags);
@@ -335,8 +338,12 @@ void calculate_steal_time(void)
        tb = mftb();
        purr = mfspr(SPRN_PURR);
        stolen = (tb - pme->tb) - (purr - pme->purr);
-       if (stolen > 0)
-               account_steal_time(current, stolen);
+       if (stolen > 0) {
+               if (idle_task(smp_processor_id()) != current)
+                       account_steal_time(stolen);
+               else
+                       account_idle_time(stolen);
+       }
        pme->tb = tb;
        pme->purr = purr;
 }

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 07283aea2e56359a88e5291336207def99084400..4a4a34caec55cdb277806b8e0ddbc787cedc1003 100644 (file)
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -55,13 +55,19 @@ void account_process_tick(struct task_struct *tsk, int user_tick)
        cputime =  S390_lowcore.system_timer >> 12;
        S390_lowcore.system_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
-       account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime);
+       if (idle_task(smp_processor_id()) != current)
+               account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime);
+       else
+               account_idle_time(cputime);
 
        cputime = S390_lowcore.steal_clock;
        if ((__s64) cputime > 0) {
                cputime >>= 12;
                S390_lowcore.steal_clock -= cputime << 12;
-               account_steal_time(tsk, cputime);
+               if (idle_task(smp_processor_id()) != current)
+                       account_steal_time(cputime);
+               else
+                       account_idle_time(cputime);
        }
 }
 
@@ -87,7 +93,10 @@ void account_vtime(struct task_struct *tsk)
        cputime =  S390_lowcore.system_timer >> 12;
        S390_lowcore.system_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
-       account_system_time(tsk, 0, cputime, cputime);
+       if (idle_task(smp_processor_id()) != current)
+               account_system_time(tsk, 0, cputime, cputime);
+       else
+               account_idle_time(cputime);
 }
 
 /*
@@ -107,7 +116,10 @@ void account_system_vtime(struct task_struct *tsk)
        cputime =  S390_lowcore.system_timer >> 12;
        S390_lowcore.system_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
-       account_system_time(tsk, 0, cputime, cputime);
+       if (in_irq() || idle_task(smp_processor_id()) != current)
+               account_system_time(tsk, 0, cputime, cputime);
+       else
+               account_idle_time(cputime);
 }
 EXPORT_SYMBOL_GPL(account_system_vtime);
 

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index c9f7cda48ed78ecbe1b421c540bbe2b777681400..732e52dc991ab0e03c525724a58359f4d758c3b6 100644 (file)
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -132,8 +132,7 @@ static void do_stolen_accounting(void)
        *snap = state;
 
        /* Add the appropriate number of ticks of stolen time,
-          including any left-overs from last time.  Passing NULL to
-          account_steal_time accounts the time as stolen. */
+          including any left-overs from last time. */
        stolen = runnable + offline + __get_cpu_var(residual_stolen);
 
        if (stolen < 0)
@@ -141,11 +140,10 @@ static void do_stolen_accounting(void)
 
        ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);
        __get_cpu_var(residual_stolen) = stolen;
-       account_steal_time(NULL, ticks);
+       account_steal_ticks(ticks);
 
        /* Add the appropriate number of ticks of blocked time,
-          including any left-overs from last time.  Passing idle to
-          account_steal_time accounts the time as idle/wait. */
+          including any left-overs from last time. */
        blocked += __get_cpu_var(residual_blocked);
 
        if (blocked < 0)
@@ -153,7 +151,7 @@ static void do_stolen_accounting(void)
 
        ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);
        __get_cpu_var(residual_blocked) = blocked;
-       account_steal_time(idle_task(smp_processor_id()), ticks);
+       account_idle_ticks(ticks);
 }
 
 /*

diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index c78a459662a62c5d711c754876092ef9fa852986..570d2041311911352da76c830073f7c9aa314457 100644 (file)
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -81,6 +81,11 @@ static inline unsigned int kstat_irqs(unsigned int irq)
 extern unsigned long long task_delta_exec(struct task_struct *);
 extern void account_user_time(struct task_struct *, cputime_t, cputime_t);
 extern void account_system_time(struct task_struct *, int, cputime_t, cputime_t);
-extern void account_steal_time(struct task_struct *, cputime_t);
+extern void account_steal_time(cputime_t);
+extern void account_idle_time(cputime_t);
+
+extern void account_process_tick(struct task_struct *, int user);
+extern void account_steal_ticks(unsigned long ticks);
+extern void account_idle_ticks(unsigned long ticks);
 
 #endif /* _LINUX_KERNEL_STAT_H */

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8395e715809d382bb7f3a5ed7087173e99cd15d2..b475d4db8053c9f8a6ffe8d53080276722fce2b9 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -284,7 +284,6 @@ long io_schedule_timeout(long timeout);
 
 extern void cpu_init (void);
 extern void trap_init(void);
-extern void account_process_tick(struct task_struct *task, int user);
 extern void update_process_times(int user);
 extern void scheduler_tick(void);
 

diff --git a/kernel/sched.c b/kernel/sched.c
index 5b03679ff712930027c11ad9eda5ebbccd7cb691..635eaffe1e4cb643eccbd42f1c085a86b8f2adaa 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4139,7 +4139,6 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
                         cputime_t cputime, cputime_t cputime_scaled)
 {
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
-       struct rq *rq = this_rq();
        cputime64_t tmp;
 
        if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
@@ -4158,37 +4157,84 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
                cpustat->irq = cputime64_add(cpustat->irq, tmp);
        else if (softirq_count())
                cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
-       else if (p != rq->idle)
-               cpustat->system = cputime64_add(cpustat->system, tmp);
-       else if (atomic_read(&rq->nr_iowait) > 0)
-               cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
        else
-               cpustat->idle = cputime64_add(cpustat->idle, tmp);
+               cpustat->system = cputime64_add(cpustat->system, tmp);
+
        /* Account for system time used */
        acct_update_integrals(p);
 }
 
 /*
  * Account for involuntary wait time.
- * @p: the process from which the cpu time has been stolen
  * @steal: the cpu time spent in involuntary wait
  */
-void account_steal_time(struct task_struct *p, cputime_t steal)
+void account_steal_time(cputime_t cputime)
+{
+       struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
+       cputime64_t cputime64 = cputime_to_cputime64(cputime);
+
+       cpustat->steal = cputime64_add(cpustat->steal, cputime64);
+}
+
+/*
+ * Account for idle time.
+ * @cputime: the cpu time spent in idle wait
+ */
+void account_idle_time(cputime_t cputime)
 {
        struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
-       cputime64_t tmp = cputime_to_cputime64(steal);
+       cputime64_t cputime64 = cputime_to_cputime64(cputime);
        struct rq *rq = this_rq();
 
-       if (p == rq->idle) {
-               p->stime = cputime_add(p->stime, steal);
-               if (atomic_read(&rq->nr_iowait) > 0)
-                       cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
-               else
-                       cpustat->idle = cputime64_add(cpustat->idle, tmp);
-       } else
-               cpustat->steal = cputime64_add(cpustat->steal, tmp);
+       if (atomic_read(&rq->nr_iowait) > 0)
+               cpustat->iowait = cputime64_add(cpustat->iowait, cputime64);
+       else
+               cpustat->idle = cputime64_add(cpustat->idle, cputime64);
+}
+
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
+
+/*
+ * Account a single tick of cpu time.
+ * @p: the process that the cpu time gets accounted to
+ * @user_tick: indicates if the tick is a user or a system tick
+ */
+void account_process_tick(struct task_struct *p, int user_tick)
+{
+       cputime_t one_jiffy = jiffies_to_cputime(1);
+       cputime_t one_jiffy_scaled = cputime_to_scaled(one_jiffy);
+       struct rq *rq = this_rq();
+
+       if (user_tick)
+               account_user_time(p, one_jiffy, one_jiffy_scaled);
+       else if (p != rq->idle)
+               account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
+                                   one_jiffy_scaled);
+       else
+               account_idle_time(one_jiffy);
+}
+
+/*
+ * Account multiple ticks of steal time.
+ * @p: the process from which the cpu time has been stolen
+ * @ticks: number of stolen ticks
+ */
+void account_steal_ticks(unsigned long ticks)
+{
+       account_steal_time(jiffies_to_cputime(ticks));
+}
+
+/*
+ * Account multiple ticks of idle time.
+ * @ticks: number of stolen ticks
+ */
+void account_idle_ticks(unsigned long ticks)
+{
+       account_idle_time(jiffies_to_cputime(ticks));
 }
 
+#endif
+
 /*
  * Use precise platform statistics if available:
  */

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 1f2fce2479fef78cc6ce8113d15d07ee71377e6e..611fa4c0baab39636baeae7788d5ab9007be16ea 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -419,8 +419,9 @@ void tick_nohz_restart_sched_tick(void)
 {
        int cpu = smp_processor_id();
        struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
        unsigned long ticks;
-       cputime_t cputime;
+#endif
        ktime_t now;
 
        local_irq_disable();
@@ -442,6 +443,7 @@ void tick_nohz_restart_sched_tick(void)
        tick_do_update_jiffies64(now);
        cpu_clear(cpu, nohz_cpu_mask);
 
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
        /*
         * We stopped the tick in idle. Update process times would miss the
         * time we slept as update_process_times does only a 1 tick
@@ -451,12 +453,9 @@ void tick_nohz_restart_sched_tick(void)
        /*
         * We might be one off. Do not randomly account a huge number of ticks!
         */
-       if (ticks && ticks < LONG_MAX) {
-               add_preempt_count(HARDIRQ_OFFSET);
-               cputime = jiffies_to_cputime(ticks);
-               account_system_time(current, HARDIRQ_OFFSET, cputime, cputime);
-               sub_preempt_count(HARDIRQ_OFFSET);
-       }
+       if (ticks && ticks < LONG_MAX)
+               account_idle_ticks(ticks);
+#endif
 
        touch_softlockup_watchdog();
        /*

diff --git a/kernel/timer.c b/kernel/timer.c
index b5efb528aa1dcd1aaa878a1b81aff597e60b0f9c..dee3f641a7a72d5ec8f00c6ff07d64f0e1470385 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1018,19 +1018,6 @@ unsigned long get_next_timer_interrupt(unsigned long now)
 }
 #endif
 
-#ifndef CONFIG_VIRT_CPU_ACCOUNTING
-void account_process_tick(struct task_struct *p, int user_tick)
-{
-       cputime_t one_jiffy = jiffies_to_cputime(1);
-
-       if (user_tick)
-               account_user_time(p, one_jiffy, cputime_to_scaled(one_jiffy));
-       else
-               account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
-                                   cputime_to_scaled(one_jiffy));
-}
-#endif
-
 /*
  * Called from the timer interrupt handler to charge one tick to the current
  * process.  user_tick is 1 if the tick is user time, 0 for system.