Re: [Xen-devel] [PATCH 2/2] xen: sched: rtds: use non-atomic bit-ops

[Meng Xu]

On Sun, May 15, 2016 at 7:54 PM, Tianyang Chen  wrote:
> Vcpu flags are checked and cleared atomically. Performance can be
> improved with corresponding non-atomic versions since schedule.c
> already has spin_locks in place.
>
> Signed-off-by: Tianyang Chen 

Reviewed-by: Meng Xu 

Thanks,

Meng
---
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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[Xen-devel] [PATCH 2/2] xen: sched: rtds: use non-atomic bit-ops

[Tianyang Chen]

Vcpu flags are checked and cleared atomically. Performance can be
improved with corresponding non-atomic versions since schedule.c
already has spin_locks in place.

Signed-off-by: Tianyang Chen 
---
 xen/common/sched_rt.c |   16 
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 1584d53..1a18f6d 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -936,7 +936,7 @@ burn_budget(const struct scheduler *ops, struct rt_vcpu 
*svc, s_time_t now)
 if ( svc->cur_budget <= 0 )
 {
 svc->cur_budget = 0;
-set_bit(__RTDS_depleted, >flags);
+__set_bit(__RTDS_depleted, >flags);
 }
 
 /* TRACE */
@@ -1050,7 +1050,7 @@ rt_schedule(const struct scheduler *ops, s_time_t now, 
bool_t tasklet_work_sched
 if ( snext != scurr &&
  !is_idle_vcpu(current) &&
  vcpu_runnable(current) )
-set_bit(__RTDS_delayed_runq_add, >flags);
+__set_bit(__RTDS_delayed_runq_add, >flags);
 
 snext->last_start = now;
 ret.time =  -1; /* if an idle vcpu is picked */
@@ -1059,7 +1059,7 @@ rt_schedule(const struct scheduler *ops, s_time_t now, 
bool_t tasklet_work_sched
 if ( snext != scurr )
 {
 q_remove(snext);
-set_bit(__RTDS_scheduled, >flags);
+__set_bit(__RTDS_scheduled, >flags);
 }
 if ( snext->vcpu->processor != cpu )
 {
@@ -1093,7 +1093,7 @@ rt_vcpu_sleep(const struct scheduler *ops, struct vcpu 
*vc)
 replq_remove(ops, svc);
 }
 else if ( svc->flags & RTDS_delayed_runq_add )
-clear_bit(__RTDS_delayed_runq_add, >flags);
+__clear_bit(__RTDS_delayed_runq_add, >flags);
 }
 
 /*
@@ -1235,7 +1235,7 @@ rt_vcpu_wake(const struct scheduler *ops, struct vcpu *vc)
  */
 if ( unlikely(svc->flags & RTDS_scheduled) )
 {
-set_bit(__RTDS_delayed_runq_add, >flags);
+__set_bit(__RTDS_delayed_runq_add, >flags);
 /*
  * The vcpu is waking up already, and we didn't even had the time to
  * remove its next replenishment event from the replenishment queue
@@ -1266,12 +1266,12 @@ rt_context_saved(const struct scheduler *ops, struct 
vcpu *vc)
 struct rt_vcpu *svc = rt_vcpu(vc);
 spinlock_t *lock = vcpu_schedule_lock_irq(vc);
 
-clear_bit(__RTDS_scheduled, >flags);
+__clear_bit(__RTDS_scheduled, >flags);
 /* not insert idle vcpu to runq */
 if ( is_idle_vcpu(vc) )
 goto out;
 
-if ( test_and_clear_bit(__RTDS_delayed_runq_add, >flags) &&
+if ( __test_and_clear_bit(__RTDS_delayed_runq_add, >flags) &&
  likely(vcpu_runnable(vc)) )
 {
 runq_insert(ops, svc);
@@ -1447,7 +1447,7 @@ static void repl_timer_handler(void *data){
 runq_tickle(ops, next_on_runq);
 }
 else if ( vcpu_on_q(svc) &&
-  test_and_clear_bit(__RTDS_depleted, >flags) )
+  __test_and_clear_bit(__RTDS_depleted, >flags) )
 runq_tickle(ops, svc);
 
 list_del(>replq_elem);
-- 
1.7.9.5


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