[Xen-devel] [RFC 1/9] schedule: Introduce per-pcpu time accounting

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

From: Andrii Anisov <andrii_anisov@xxxxxxxx>

Introduce per-pcpu time accounting what includes the following states:

TACC_HYP - the pcpu executes hypervisor code like softirq processing
           (including scheduling), tasklets and context switches
TACC_GUEST - the pcpu executes guests code
TACC_IDLE - the low-power state of the pcpu
TACC_IRQ - the pcpu performs interrupts processing, without separation to
           guest or hypervisor interrupts
TACC_GSYNC - the pcpu executes hypervisor code to process synchronous trap
             from the guest. E.g. hypercall processing or io emulation.

Currently, the only reenterant state is TACC_IRQ. It is assumed, no changes
to state other than TACC_IRQ could happen until we return from nested
interrupts. IRQ time is accounted in a distinct way comparing to other states.
It is acumulated between other states transition moments, and is substracted
from the old state on states transion calculation.

Signed-off-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
---
 xen/common/schedule.c   | 81 +++++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/sched.h | 27 +++++++++++++++++
 2 files changed, 108 insertions(+)

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 7b71581..6dd6603 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -1539,6 +1539,87 @@ static void schedule(void)
     context_switch(prev, next);
 }
 
+DEFINE_PER_CPU(struct tacc, tacc);
+
+static void tacc_state_change(enum TACC_STATES new_state)
+{
+    s_time_t now, delta;
+    struct tacc* tacc = &this_cpu(tacc);
+    unsigned long flags;
+
+    local_irq_save(flags);
+
+    now = NOW();
+    delta = now - tacc->state_entry_time;
+
+    /* We do not expect states reenterability (at least through this 
function)*/
+    ASSERT(new_state != tacc->state);
+
+    tacc->state_time[tacc->state] += delta - tacc->irq_time;
+    tacc->state_time[TACC_IRQ] += tacc->irq_time;
+    tacc->irq_time = 0;
+    tacc->state = new_state;
+    tacc->state_entry_time = now;
+
+    local_irq_restore(flags);
+}
+
+void tacc_hyp(int place)
+{
+//    printk("\ttacc_hyp %u, place %d\n", smp_processor_id(), place);
+    tacc_state_change(TACC_HYP);
+}
+
+void tacc_guest(int place)
+{
+//    printk("\ttacc_guest %u, place %d\n", smp_processor_id(), place);
+    tacc_state_change(TACC_GUEST);
+}
+
+void tacc_idle(int place)
+{
+//    printk("\tidle cpu %u, place %d\n", smp_processor_id(), place);
+    tacc_state_change(TACC_IDLE);
+}
+
+void tacc_gsync(int place)
+{
+//    printk("\ttacc_gsync %u, place %d\n", smp_processor_id(), place);
+    tacc_state_change(TACC_GSYNC);
+}
+
+void tacc_irq_enter(int place)
+{
+    struct tacc* tacc = &this_cpu(tacc);
+
+//    printk("\ttacc_irq_enter %u, place %d, cnt %d\n", smp_processor_id(), 
place, this_cpu(tacc).irq_cnt);
+    ASSERT(!local_irq_is_enabled());
+    ASSERT(tacc->irq_cnt >= 0);
+
+    if ( tacc->irq_cnt == 0 )
+    {
+        tacc->irq_enter_time = NOW();
+    }
+
+    tacc->irq_cnt++;
+}
+
+void tacc_irq_exit(int place)
+{
+    struct tacc* tacc = &this_cpu(tacc);
+
+//    printk("\ttacc_irq_exit %u, place %d, cnt %d\n", smp_processor_id(), 
place, tacc->irq_cnt);
+    ASSERT(!local_irq_is_enabled());
+    ASSERT(tacc->irq_cnt > 0);
+    if ( tacc->irq_cnt == 1 )
+    {
+        tacc->irq_time = NOW() - tacc->irq_enter_time;
+        tacc->irq_enter_time = 0;
+    }
+
+    tacc->irq_cnt--;
+}
+
 void context_saved(struct vcpu *prev)
 {
     /* Clear running flag /after/ writing context to memory. */
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index e3601c1..04a8724 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -1002,6 +1002,33 @@ extern void dump_runq(unsigned char key);
 
 void arch_do_physinfo(struct xen_sysctl_physinfo *pi);
 
+enum TACC_STATES {
+    TACC_HYP = 0,
+    TACC_GUEST = 1,
+    TACC_IDLE = 2,
+    TACC_IRQ = 3,
+    TACC_GSYNC = 4,
+    TACC_STATES_MAX
+};
+
+struct tacc
+{
+    s_time_t state_time[TACC_STATES_MAX];
+    s_time_t state_entry_time;
+    int state;
+
+    s_time_t guest_time;
+
+    s_time_t irq_enter_time;
+    s_time_t irq_time;
+    int irq_cnt;
+};
+
+DECLARE_PER_CPU(struct tacc, tacc);
+
+void tacc_hyp(int place);
+void tacc_idle(int place);
+
 #endif /* __SCHED_H__ */
 
 /*
-- 
2.7.4


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