[RFC,8/9] sched:credit: get guest time from time accounting code

Commit Message

Andrii Anisov Sept. 11, 2019, 10:32 a.m. UTC

From: Andrii Anisov <[e-mail]>

While the Credit scheduler code uses guest time from the
other pcpu, we have to use locked time accounting.

Signed-off-by: Andrii Anisov <[e-mail]>
---
 xen/common/Kconfig        |  1 +
 xen/common/sched_credit.c | 12 +++++-------
 2 files changed, 6 insertions(+), 7 deletions(-)

Patch

diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index c1748dd..d17a8b4 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -227,6 +227,7 @@  config TACC_NEEDS_LOCK
 config SCHED_CREDIT
 	bool "Credit scheduler support"
 	default y
+	select TACC_NEEDS_LOCK
 	---help---
 	  The traditional credit scheduler is a general purpose scheduler.
 
diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index 81dee5e..ac6b9e6 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -324,16 +324,15 @@  runq_remove(struct csched_vcpu *svc)
     __runq_remove(svc);
 }
 
-static void burn_credits(struct csched_vcpu *svc, s_time_t now)
+static void burn_credits(struct csched_vcpu *svc, s_time_t delta)
 {
-    s_time_t delta;
     uint64_t val;
     unsigned int credits;
 
     /* Assert svc is current */
     ASSERT( svc == CSCHED_VCPU(curr_on_cpu(svc->vcpu->processor)) );
 
-    if ( (delta = now - svc->start_time) <= 0 )
+    if ( delta <= 0 )
         return;
 
     val = delta * CSCHED_CREDITS_PER_MSEC + svc->residual;
@@ -341,7 +340,6 @@  static void burn_credits(struct csched_vcpu *svc, s_time_t now)
     credits = val;
     ASSERT(credits == val); /* make sure we haven't truncated val */
     atomic_sub(credits, &svc->credit);
-    svc->start_time += (credits * MILLISECS(1)) / CSCHED_CREDITS_PER_MSEC;
 }
 
 static bool_t __read_mostly opt_tickle_one_idle = 1;
@@ -956,7 +954,7 @@  csched_vcpu_acct(struct csched_private *prv, unsigned int cpu)
     /*
      * Update credits
      */
-    burn_credits(svc, NOW());
+    burn_credits(svc, tacc_get_guest_time_delta_vcpu(svc->vcpu));
 
     /*
      * Put this VCPU and domain back on the active list if it was
@@ -1856,14 +1854,14 @@  csched_schedule(
                     (unsigned char *)&d);
     }
 
-    runtime = now - current->runstate.state_entry_time;
+    runtime = tacc_get_guest_time_delta();
     if ( runtime < 0 ) /* Does this ever happen? */
         runtime = 0;
 
     if ( !is_idle_vcpu(scurr->vcpu) )
     {
         /* Update credits of a non-idle VCPU. */
-        burn_credits(scurr, now);
+        burn_credits(scurr, runtime);
         scurr->start_time -= now;
         scurr->last_sched_time = now;
     }