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KVM guest: Steal time accounting

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This patch accounts steal time time in account_process_tick.
If one or more tick is considered stolen in the current
accounting cycle, user/system accounting is skipped. Idle is fine,
since the hypervisor does not report steal time if the guest
is halted.

Accounting steal time from the core scheduler give us the
advantage of direct acess to the runqueue data. In a later
opportunity, it can be used to tweak cpu power and make
the scheduler aware of the time it lost.

[avi: <asm/paravirt.h> doesn't exist on many archs]

Signed-off-by: Glauber Costa <glommer@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Eric B Munson <emunson@mgebm.net>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
CC: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Glauber Costa 2011-07-11 15:28:17 -04:00 committed by Avi Kivity
parent 747f292583
commit e6e6685acc
1 changed files with 43 additions and 0 deletions
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43
kernel/sched.c
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@ -75,6 +75,9 @@
#include <asm/tlb.h>
#include <asm/irq_regs.h>
#include <asm/mutex.h>
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#endif
#include "sched_cpupri.h"
#include "workqueue_sched.h"
@ -528,6 +531,9 @@ struct rq {
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
u64 prev_irq_time;
#endif
#ifdef CONFIG_PARAVIRT
u64 prev_steal_time;
#endif
/* calc_load related fields */
unsigned long calc_load_update;
@ -1953,6 +1959,18 @@ void account_system_vtime(struct task_struct *curr)
}
EXPORT_SYMBOL_GPL(account_system_vtime);
#endif /* CONFIG_IRQ_TIME_ACCOUNTING */
#ifdef CONFIG_PARAVIRT
static inline u64 steal_ticks(u64 steal)
{
if (unlikely(steal > NSEC_PER_SEC))
return div_u64(steal, TICK_NSEC);
return __iter_div_u64_rem(steal, TICK_NSEC, &steal);
}
#endif
static void update_rq_clock_task(struct rq *rq, s64 delta)
{
s64 irq_delta;
@ -3845,6 +3863,25 @@ void account_idle_time(cputime_t cputime)
cpustat->idle = cputime64_add(cpustat->idle, cputime64);
}
static __always_inline bool steal_account_process_tick(void)
{
#ifdef CONFIG_PARAVIRT
if (static_branch(&paravirt_steal_enabled)) {
u64 steal, st = 0;
steal = paravirt_steal_clock(smp_processor_id());
steal -= this_rq()->prev_steal_time;
st = steal_ticks(steal);
this_rq()->prev_steal_time += st * TICK_NSEC;
account_steal_time(st);
return st;
}
#endif
return false;
}
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
@ -3876,6 +3913,9 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
cputime64_t tmp = cputime_to_cputime64(cputime_one_jiffy);
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
if (steal_account_process_tick())
return;
if (irqtime_account_hi_update()) {
cpustat->irq = cputime64_add(cpustat->irq, tmp);
} else if (irqtime_account_si_update()) {
@ -3929,6 +3969,9 @@ void account_process_tick(struct task_struct *p, int user_tick)
return;
}
if (steal_account_process_tick())
return;
if (user_tick)
account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))