[PATCH] xen/sched: try harder to find a runnable unit in rt_schedule()

* [PATCH] xen/sched: try harder to find a runnable unit in rt_schedule()
@ 2022-10-21 10:39 Juergen Gross
  2022-11-04  7:51 ` Dario Faggioli
  0 siblings, 1 reply; 2+ messages in thread
From: Juergen Gross @ 2022-10-21 10:39 UTC (permalink / raw)
  To: xen-devel; +Cc: Juergen Gross, Dario Faggioli, Meng Xu, George Dunlap

Instead of directly falling back to the idle unit in case the top
unit from the run queue happened to be not runnable, consult the run
queue again.

Suggested-by: Dario Faggioli <dfaggioli@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 xen/common/sched/rt.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/xen/common/sched/rt.c b/xen/common/sched/rt.c
index 960a8033e2..1f8d074884 100644
--- a/xen/common/sched/rt.c
+++ b/xen/common/sched/rt.c
@@ -1080,15 +1080,20 @@ rt_schedule(const struct scheduler *ops, struct sched_unit *currunit,
     }
     else
     {
-        snext = runq_pick(ops, cpumask_of(sched_cpu), cur_cpu);
-
-        if ( snext == NULL )
-            snext = rt_unit(sched_idle_unit(sched_cpu));
-        else if ( !unit_runnable_state(snext->unit) )
+        while ( true )
         {
+            snext = runq_pick(ops, cpumask_of(sched_cpu), cur_cpu);
+
+            if ( snext == NULL )
+            {
+                snext = rt_unit(sched_idle_unit(sched_cpu));
+                break;
+            }
+            if ( unit_runnable_state(snext->unit) )
+                break;
+
             q_remove(snext);
             replq_remove(ops, snext);
-            snext = rt_unit(sched_idle_unit(sched_cpu));
         }
 
         /* if scurr has higher priority and budget, still pick scurr */
-- 
2.35.3



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