Re: [Xen-devel] [PATCH 2/5] xen: use masking operation instead of test_bit for CSFLAG bits

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 02/10/15 05:40, Juergen Gross wrote:
> Use a bit mask for testing of a set bit instead of test_bit in case no
> atomic operation is needed, as this will lead to smaller and more
> effective code.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>

> ---
>  xen/common/sched_credit2.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index bf1fe6f..912e1a2 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -418,7 +418,7 @@ __runq_insert(struct list_head *runq, struct csched2_vcpu 
> *svc)
>      /* Idle vcpus not allowed on the runqueue anymore */
>      BUG_ON(is_idle_vcpu(svc->vcpu));
>      BUG_ON(svc->vcpu->is_running);
> -    BUG_ON(test_bit(__CSFLAG_scheduled, &svc->flags));
> +    BUG_ON(svc->flags & CSFLAG_scheduled);
>  
>      list_for_each( iter, runq )
>      {
> @@ -844,7 +844,7 @@ static void
>  __runq_deassign(struct csched2_vcpu *svc)
>  {
>      BUG_ON(__vcpu_on_runq(svc));
> -    BUG_ON(test_bit(__CSFLAG_scheduled, &svc->flags));
> +    BUG_ON(svc->flags & CSFLAG_scheduled);
>  
>      list_del_init(&svc->rqd_elem);
>      update_max_weight(svc->rqd, 0, svc->weight);
> @@ -952,7 +952,7 @@ csched2_vcpu_sleep(const struct scheduler *ops, struct 
> vcpu *vc)
>          update_load(ops, svc->rqd, svc, -1, NOW());
>          __runq_remove(svc);
>      }
> -    else if ( test_bit(__CSFLAG_delayed_runq_add, &svc->flags) )
> +    else if ( svc->flags & CSFLAG_delayed_runq_add )
>          clear_bit(__CSFLAG_delayed_runq_add, &svc->flags);
>  }
>  
> @@ -988,7 +988,7 @@ csched2_vcpu_wake(const struct scheduler *ops, struct 
> vcpu *vc)
>      /* If the context hasn't been saved for this vcpu yet, we can't put it on
>       * another runqueue.  Instead, we set a flag so that it will be put on 
> the runqueue
>       * after the context has been saved. */
> -    if ( unlikely (test_bit(__CSFLAG_scheduled, &svc->flags) ) )
> +    if ( unlikely(svc->flags & CSFLAG_scheduled) )
>      {
>          set_bit(__CSFLAG_delayed_runq_add, &svc->flags);
>          goto out;
> @@ -1204,7 +1204,7 @@ static void migrate(const struct scheduler *ops,
>                      struct csched2_runqueue_data *trqd, 
>                      s_time_t now)
>  {
> -    if ( test_bit(__CSFLAG_scheduled, &svc->flags) )
> +    if ( svc->flags & CSFLAG_scheduled )
>      {
>          d2printk("%pv %d-%d a\n", svc->vcpu, svc->rqd->id, trqd->id);
>          /* It's running; mark it to migrate. */
> @@ -1348,7 +1348,7 @@ retry:
>          __update_svc_load(ops, push_svc, 0, now);
>  
>          /* Skip this one if it's already been flagged to migrate */
> -        if ( test_bit(__CSFLAG_runq_migrate_request, &push_svc->flags) )
> +        if ( push_svc->flags & CSFLAG_runq_migrate_request )
>              continue;
>  
>          list_for_each( pull_iter, &st.orqd->svc )
> @@ -1361,7 +1361,7 @@ retry:
>              }
>          
>              /* Skip this one if it's already been flagged to migrate */
> -            if ( test_bit(__CSFLAG_runq_migrate_request, &pull_svc->flags) )
> +            if ( pull_svc->flags & CSFLAG_runq_migrate_request )
>                  continue;
>  
>              consider(&st, push_svc, pull_svc);
> @@ -1378,7 +1378,7 @@ retry:
>          struct csched2_vcpu * pull_svc = list_entry(pull_iter, struct 
> csched2_vcpu, rqd_elem);
>          
>          /* Skip this one if it's already been flagged to migrate */
> -        if ( test_bit(__CSFLAG_runq_migrate_request, &pull_svc->flags) )
> +        if ( pull_svc->flags & CSFLAG_runq_migrate_request )
>              continue;
>  
>          /* Consider pull only */
> 


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