cpuidle: suspend/resume scheduler tick timer during cpu idle state entry/exit

cpuidle can collaborate with scheduler to reduce unnecessary timer
interrupt. For example, credit scheduler accounting timer
doesn't need to be active at idle time, so it can be stopped at
cpuidle entry and resumed at cpuidle exit. This patch implements this
function by adding two ops in scheduler: tick_suspend/tick_resume, and
implement them for credit scheduler

Signed-off-by: Yu Ke <ke.yu@intel.com>
Signed-off-by: Tian Kevin <kevin.tian@intel.com>

diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index f8302d1f54627b2bf97306af05b777284915e537..40263873e8d6348bcb4b2ca05445bb3e7579e40f 100644 (file)
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -195,6 +195,15 @@ static void acpi_processor_idle(void)
     int sleep_ticks = 0;
     u32 t1, t2 = 0;
 
+    sched_tick_suspend();
+    /*
+     * sched_tick_suspend may raise TIMER_SOFTIRQ by __stop_timer,
+     * which will break the later assumption of no sofirq pending,
+     * so add do_softirq
+     */
+    if ( softirq_pending(smp_processor_id()) )
+        do_softirq();
+
     /*
      * Interrupts must be disabled during bus mastering calculations and
      * for C2/C3 transitions.
@@ -204,6 +213,7 @@ static void acpi_processor_idle(void)
     if ( softirq_pending(smp_processor_id()) )
     {
         local_irq_enable();
+        sched_tick_resume();
         return;
     }
 
@@ -223,6 +233,7 @@ static void acpi_processor_idle(void)
             pm_idle_save();
         else
             acpi_safe_halt();
+        sched_tick_resume();
         return;
     }
 
@@ -329,6 +340,7 @@ static void acpi_processor_idle(void)
 
     default:
         local_irq_enable();
+        sched_tick_resume();
         return;
     }
 
@@ -339,6 +351,8 @@ static void acpi_processor_idle(void)
         cx->time += sleep_ticks;
     }
 
+    sched_tick_resume();
+
     if ( cpuidle_current_governor->reflect )
         cpuidle_current_governor->reflect(power);
 }

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index d724293bc164496c59289bc58763f5ac4d6c4e8f..c554c8b8b9bd0482bdda38b2674ad46521bf4a1b 100644 (file)
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -154,6 +154,7 @@ struct csched_private {
     spinlock_t lock;
     struct list_head active_sdom;
     uint32_t ncpus;
+    struct timer  master_ticker;
     unsigned int master;
     cpumask_t idlers;
     uint32_t weight;
@@ -757,7 +758,7 @@ csched_runq_sort(unsigned int cpu)
 }
 
 static void
-csched_acct(void)
+csched_acct(void* dummy)
 {
     unsigned long flags;
     struct list_head *iter_vcpu, *next_vcpu;
@@ -792,7 +793,7 @@ csched_acct(void)
         csched_priv.credit_balance = 0;
         spin_unlock_irqrestore(&csched_priv.lock, flags);
         CSCHED_STAT_CRANK(acct_no_work);
-        return;
+        goto out;
     }
 
     CSCHED_STAT_CRANK(acct_run);
@@ -950,6 +951,10 @@ csched_acct(void)
 
     /* Inform each CPU that its runq needs to be sorted */
     csched_priv.runq_sort++;
+
+out:
+    set_timer( &csched_priv.master_ticker, NOW() +
+            MILLISECS(CSCHED_MSECS_PER_TICK) * CSCHED_TICKS_PER_ACCT );
 }
 
 static void
@@ -966,18 +971,6 @@ csched_tick(void *_cpu)
     if ( !is_idle_vcpu(current) )
         csched_vcpu_acct(cpu);
 
-    /*
-     * Host-wide accounting duty
-     *
-     * Note: Currently, this is always done by the master boot CPU. Eventually,
-     * we could distribute or at the very least cycle the duty.
-     */
-    if ( (csched_priv.master == cpu) &&
-         (spc->tick % CSCHED_TICKS_PER_ACCT) == 0 )
-    {
-        csched_acct();
-    }
-
     /*
      * Check if runq needs to be sorted
      *
@@ -1310,10 +1303,35 @@ static __init int csched_start_tickers(void)
         set_timer(&spc->ticker, NOW() + MILLISECS(CSCHED_MSECS_PER_TICK));
     }
 
+    init_timer( &csched_priv.master_ticker, csched_acct, NULL,
+                    csched_priv.master);
+
+    set_timer( &csched_priv.master_ticker, NOW() +
+            MILLISECS(CSCHED_MSECS_PER_TICK) * CSCHED_TICKS_PER_ACCT );
+
     return 0;
 }
 __initcall(csched_start_tickers);
 
+static void csched_tick_suspend(void)
+{
+    struct csched_pcpu *spc;
+
+    spc = CSCHED_PCPU(smp_processor_id());
+
+    stop_timer(&spc->ticker);
+}
+
+static void csched_tick_resume(void)
+{
+    struct csched_pcpu *spc;
+    uint64_t now = NOW();
+
+    spc = CSCHED_PCPU(smp_processor_id());
+
+    set_timer(&spc->ticker, now + MILLISECS(CSCHED_MSECS_PER_TICK)
+            - now % MILLISECS(CSCHED_MSECS_PER_TICK) );
+}
 
 struct scheduler sched_credit_def = {
     .name           = "SMP Credit Scheduler",
@@ -1337,4 +1355,7 @@ struct scheduler sched_credit_def = {
     .dump_cpu_state = csched_dump_pcpu,
     .dump_settings  = csched_dump,
     .init           = csched_init,
+
+    .tick_suspend   = csched_tick_suspend,
+    .tick_resume    = csched_tick_resume,
 };

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 5e91f6c85d818744f981f29010925241bb471b8b..f1121938da94311d8af56d9ed87b907a13120e3a 100644 (file)
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -964,6 +964,16 @@ void dump_runq(unsigned char key)
     local_irq_restore(flags);
 }
 
+void sched_tick_suspend(void)
+{
+    SCHED_OP(tick_suspend);
+}
+
+void sched_tick_resume(void)
+{
+    SCHED_OP(tick_resume);
+}
+
 #ifdef CONFIG_COMPAT
 #include "compat/schedule.c"
 #endif

diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h
index f6ba9faa5c41fde699950e8bfbd35266ee77eca1..5caf8245d2079d98ec277ac22d2e4438e70f0700 100644 (file)
--- a/xen/include/xen/sched-if.h
+++ b/xen/include/xen/sched-if.h
@@ -77,6 +77,9 @@ struct scheduler {
                                     struct xen_domctl_scheduler_op *);
     void         (*dump_settings)  (void);
     void         (*dump_cpu_state) (int);
+
+    void         (*tick_suspend)    (void);
+    void         (*tick_resume)     (void);
 };
 
 #endif /* __XEN_SCHED_IF_H__ */

diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index efaec7e9b7fa66902991dd53e707dc2e2c407653..206bf6de4e6edabfa5b8070301ed95230533dc20 100644 (file)
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -428,6 +428,8 @@ int  sched_init_domain(struct domain *d);
 void sched_destroy_domain(struct domain *d);
 long sched_adjust(struct domain *, struct xen_domctl_scheduler_op *);
 int  sched_id(void);
+void sched_tick_suspend(void);
+void sched_tick_resume(void);
 void vcpu_wake(struct vcpu *d);
 void vcpu_sleep_nosync(struct vcpu *d);
 void vcpu_sleep_sync(struct vcpu *d);