[Xen-devel] [RFC 7/9] tacc: Introduce a locked interface for guest time

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

From: Andrii Anisov <andrii_anisov@xxxxxxxx>

The locked interface to acquire guest time by scheduling code
is introduced. It can be used by schedulers what do require
guest time from a different pcpu to take scheduling decission.

Signed-off-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
---
 xen/common/Kconfig      |  3 +++
 xen/common/schedule.c   | 44 ++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/sched.h | 11 +++++++++++
 3 files changed, 58 insertions(+)

diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 16829f6..c1748dd 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -221,6 +221,9 @@ config ARGO
 menu "Schedulers"
        visible if EXPERT = "y"
 
+config TACC_NEEDS_LOCK
+       bool
+
 config SCHED_CREDIT
        bool "Credit scheduler support"
        default y
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 62df77e..98b739f 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -1562,6 +1562,14 @@ static void schedule(void)
     context_switch(prev, next);
 }
 
+#ifdef CONFIG_TACC_NEEDS_LOCK
+#define     tacc_lock(tacc) spin_lock(&tacc->tacc_lock)
+#define     tacc_unlock(tacc) spin_unlock(&tacc->tacc_lock)
+#else
+#define     tacc_lock(tacc)
+#define     tacc_unlock(tacc)
+#endif
+
 DEFINE_PER_CPU(struct tacc, tacc);
 
 static void tacc_state_change(enum TACC_STATES new_state)
@@ -1571,6 +1579,7 @@ static void tacc_state_change(enum TACC_STATES new_state)
     unsigned long flags;
 
     local_irq_save(flags);
+    tacc_lock(tacc);
 
     now = NOW();
     delta = now - tacc->state_entry_time;
@@ -1584,6 +1593,7 @@ static void tacc_state_change(enum TACC_STATES new_state)
     tacc->state = new_state;
     tacc->state_entry_time = now;
 
+    tacc_unlock(tacc);
     local_irq_restore(flags);
 }
 
@@ -1621,7 +1631,9 @@ void tacc_irq_enter(int place)
 
     if ( tacc->irq_cnt == 0 )
     {
+        tacc_lock(tacc);
         tacc->irq_enter_time = NOW();
+        tacc_unlock(tacc);
     }
 
     tacc->irq_cnt++;
@@ -1636,8 +1648,10 @@ void tacc_irq_exit(int place)
     ASSERT(tacc->irq_cnt > 0);
     if ( tacc->irq_cnt == 1 )
     {
+        tacc_lock(tacc);
         tacc->irq_time = NOW() - tacc->irq_enter_time;
         tacc->irq_enter_time = 0;
+        tacc_unlock(tacc);
     }
 
     tacc->irq_cnt--;
@@ -1653,6 +1667,36 @@ s_time_t tacc_get_guest_time(struct tacc *tacc)
     return guest_time;
 }
 
+#ifdef CONFIG_TACC_NEEDS_LOCK
+s_time_t tacc_get_guest_time_cpu(int cpu)
+{
+    struct tacc* tacc = &per_cpu(tacc, cpu);
+    s_time_t guest_time;
+    s_time_t now;
+
+    tacc_lock(tacc);
+
+    now = NOW();
+    guest_time = tacc_get_guest_time(tacc);
+    if (tacc->state == TACC_GUEST || tacc->state == TACC_GSYNC)
+    {
+        guest_time += NOW() - tacc->state_entry_time;
+    }
+
+    if (tacc->irq_enter_time)
+    {
+        guest_time -= NOW() - tacc->irq_enter_time;
+    }
+
+    guest_time -= tacc->irq_time;
+
+    tacc_unlock(tacc);
+
+    return guest_time;
+}
+#endif
+
+
 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 5b41805..a649d1f 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -1028,6 +1028,9 @@ struct tacc
     s_time_t irq_enter_time;
     s_time_t irq_time;
     int irq_cnt;
+#ifdef CONFIG_TACC_NEEDS_LOCK
+    spinlock_t tacc_lock;
+#endif
 };
 
 DECLARE_PER_CPU(struct tacc, tacc);
@@ -1041,6 +1044,14 @@ inline s_time_t tacc_get_guest_time_delta(void)
     return tacc_get_guest_time(&this_cpu(tacc)) - current->pcpu_guest_time;
 }
 
+#ifdef CONFIG_TACC_NEEDS_LOCK
+s_time_t tacc_get_guest_time_cpu(int cpu);
+inline s_time_t tacc_get_guest_time_delta_vcpu(struct vcpu* vcpu)
+{
+    return tacc_get_guest_time_cpu(vcpu->processor) - vcpu->pcpu_guest_time;
+}
+#endif
+
 #endif /* __SCHED_H__ */
 
 /*
-- 
2.7.4


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