Re: [Xen-devel] [PATCH 16/24] xen: sched: factor affinity helpers out of sched_credit.c

[George Dunlap]

On 17/08/16 18:19, Dario Faggioli wrote:
> make it possible to use the various helpers from other
> schedulers, e.g., for implementing soft affinity within
> them.
> 
> Since we are touching the code, also make it start using
> variables called v for struct_vcpu*, as it is preferrable.
> 
> No functional change intended.
> 
> Signed-off-by: Dario Faggioli 
> Signed-off-by: Justin T. Weaver 

Reviewed-by: George Dunlap 


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[Xen-devel] [PATCH 16/24] xen: sched: factor affinity helpers out of sched_credit.c

[Dario Faggioli]

make it possible to use the various helpers from other
schedulers, e.g., for implementing soft affinity within
them.

Since we are touching the code, also make it start using
variables called v for struct_vcpu*, as it is preferrable.

No functional change intended.

Signed-off-by: Dario Faggioli 
Signed-off-by: Justin T. Weaver 
---
Cc: George Dunlap 
Cc: Anshul Makkar 
---
 xen/common/sched_credit.c  |   98 +++-
 xen/include/xen/sched-if.h |   65 +
 2 files changed, 80 insertions(+), 83 deletions(-)

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index 14b207d..5d5bba9 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -137,27 +137,6 @@
 #define TRC_CSCHED_SCHEDULE  TRC_SCHED_CLASS_EVT(CSCHED, 9)
 #define TRC_CSCHED_RATELIMIT TRC_SCHED_CLASS_EVT(CSCHED, 10)
 
-
-/*
- * Hard and soft affinity load balancing.
- *
- * Idea is each vcpu has some pcpus that it prefers, some that it does not
- * prefer but is OK with, and some that it cannot run on at all. The first
- * set of pcpus are the ones that are both in the soft affinity *and* in the
- * hard affinity; the second set of pcpus are the ones that are in the hard
- * affinity but *not* in the soft affinity; the third set of pcpus are the
- * ones that are not in the hard affinity.
- *
- * We implement a two step balancing logic. Basically, every time there is
- * the need to decide where to run a vcpu, we first check the soft affinity
- * (well, actually, the && between soft and hard affinity), to see if we can
- * send it where it prefers to (and can) run on. However, if the first step
- * does not find any suitable and free pcpu, we fall back checking the hard
- * affinity.
- */
-#define CSCHED_BALANCE_SOFT_AFFINITY0
-#define CSCHED_BALANCE_HARD_AFFINITY1
-
 /*
  * Boot parameters
  */
@@ -287,53 +266,6 @@ __runq_remove(struct csched_vcpu *svc)
 list_del_init(>runq_elem);
 }
 
-
-#define for_each_csched_balance_step(step) \
-for ( (step) = 0; (step) <= CSCHED_BALANCE_HARD_AFFINITY; (step)++ )
-
-
-/*
- * Hard affinity balancing is always necessary and must never be skipped.
- * But soft affinity need only be considered when it has a functionally
- * different effect than other constraints (such as hard affinity, cpus
- * online, or cpupools).
- *
- * Soft affinity only needs to be considered if:
- * * The cpus in the cpupool are not a subset of soft affinity
- * * The hard affinity is not a subset of soft affinity
- * * There is an overlap between the soft affinity and the mask which is
- *   currently being considered.
- */
-static inline int __vcpu_has_soft_affinity(const struct vcpu *vc,
-   const cpumask_t *mask)
-{
-return !cpumask_subset(cpupool_domain_cpumask(vc->domain),
-   vc->cpu_soft_affinity) &&
-   !cpumask_subset(vc->cpu_hard_affinity, vc->cpu_soft_affinity) &&
-   cpumask_intersects(vc->cpu_soft_affinity, mask);
-}
-
-/*
- * Each csched-balance step uses its own cpumask. This function determines
- * which one (given the step) and copies it in mask. For the soft affinity
- * balancing step, the pcpus that are not part of vc's hard affinity are
- * filtered out from the result, to avoid running a vcpu where it would
- * like, but is not allowed to!
- */
-static void
-csched_balance_cpumask(const struct vcpu *vc, int step, cpumask_t *mask)
-{
-if ( step == CSCHED_BALANCE_SOFT_AFFINITY )
-{
-cpumask_and(mask, vc->cpu_soft_affinity, vc->cpu_hard_affinity);
-
-if ( unlikely(cpumask_empty(mask)) )
-cpumask_copy(mask, vc->cpu_hard_affinity);
-}
-else /* step == CSCHED_BALANCE_HARD_AFFINITY */
-cpumask_copy(mask, vc->cpu_hard_affinity);
-}
-
 static void burn_credits(struct csched_vcpu *svc, s_time_t now)
 {
 s_time_t delta;
@@ -398,18 +330,18 @@ static inline void __runq_tickle(struct csched_vcpu *new)
  * Soft and hard affinity balancing loop. For vcpus without
  * a useful soft affinity, consider hard affinity only.
  */
-for_each_csched_balance_step( balance_step )
+for_each_affinity_balance_step( balance_step )
 {
 int new_idlers_empty;
 
-if ( balance_step == CSCHED_BALANCE_SOFT_AFFINITY
- && !__vcpu_has_soft_affinity(new->vcpu,
-  new->vcpu->cpu_hard_affinity) )
+if ( balance_step == BALANCE_SOFT_AFFINITY
+ && !has_soft_affinity(new->vcpu,
+   new->vcpu->cpu_hard_affinity) )
 continue;
 
 /* Are there idlers suitable for new (for this balance step)? */
-csched_balance_cpumask(new->vcpu, balance_step,
-