[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/6] xen: credit: (micro) optimize csched_runq_steal().
Chacking whether or not a vCPU can be 'stolen' from a peer pCPU's runqueue is relatively cheap. Therefore, let's do that as early as possible, avoiding potentially useless complex checks, and cpumask manipulations. Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx> --- Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx> --- xen/common/sched_credit.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c index 63a8675..2b13e99 100644 --- a/xen/common/sched_credit.c +++ b/xen/common/sched_credit.c @@ -708,12 +708,10 @@ static inline int __csched_vcpu_is_migrateable(struct vcpu *vc, int dest_cpu, cpumask_t *mask) { /* - * Don't pick up work that's in the peer's scheduling tail or hot on - * peer PCPU. Only pick up work that prefers and/or is allowed to run - * on our CPU. + * Don't pick up work that's or hot on peer PCPU, or that can't (or + * would prefer not to) run on cpu. */ - return !vc->is_running && - !__csched_vcpu_is_cache_hot(vc) && + return !__csched_vcpu_is_cache_hot(vc) && cpumask_test_cpu(dest_cpu, mask); } @@ -1622,7 +1620,9 @@ csched_runq_steal(int peer_cpu, int cpu, int pri, int balance_step) BUG_ON( is_idle_vcpu(vc) ); /* - * If the vcpu has no useful soft affinity, skip this vcpu. + * If the vcpu is still in peer_cpu's scheduling tail, or if it + * has no useful soft affinity, skip it. + * * In fact, what we want is to check if we have any "soft-affine * work" to steal, before starting to look at "hard-affine work". * @@ -1633,8 +1633,9 @@ csched_runq_steal(int peer_cpu, int cpu, int pri, int balance_step) * vCPUs with useful soft affinities in some sort of bitmap * or counter. */ - if ( balance_step == CSCHED_BALANCE_SOFT_AFFINITY - && !__vcpu_has_soft_affinity(vc, vc->cpu_hard_affinity) ) + if ( vc->is_running || + (balance_step == CSCHED_BALANCE_SOFT_AFFINITY + && !__vcpu_has_soft_affinity(vc, vc->cpu_hard_affinity)) ) continue; csched_balance_cpumask(vc, balance_step, cpumask_scratch); _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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