diff options
author | Jan Beulich <jbeulich@suse.com> | 2013-03-04 10:17:52 +0100 |
---|---|---|
committer | Jan Beulich <jbeulich@suse.com> | 2013-03-04 10:17:52 +0100 |
commit | e6a6fd63652814e5c36a0016c082032f798ced1f (patch) | |
tree | 9bec7408703235d88385108b44d897b450786055 /xen/common/schedule.c | |
parent | 7ffc9779aa5120c5098d938cb88f69a1dda9a0fe (diff) | |
download | xen-e6a6fd63652814e5c36a0016c082032f798ced1f.tar.gz xen-e6a6fd63652814e5c36a0016c082032f798ced1f.tar.bz2 xen-e6a6fd63652814e5c36a0016c082032f798ced1f.zip |
SEDF: avoid gathering vCPU-s on pCPU0
The introduction of vcpu_force_reschedule() in 14320:215b799fa181 was
incompatible with the SEDF scheduler: Any vCPU using
VCPUOP_stop_periodic_timer (e.g. any vCPU of half way modern PV Linux
guests) ends up on pCPU0 after that call. Obviously, running all PV
guests' (and namely Dom0's) vCPU-s on pCPU0 causes problems for those
guests rather sooner than later.
So the main thing that was clearly wrong (and bogus from the beginning)
was the use of cpumask_first() in sedf_pick_cpu(). It is being replaced
by a construct that prefers to put back the vCPU on the pCPU that it
got launched on.
However, there's one more glitch: When reducing the affinity of a vCPU
temporarily, and then widening it again to a set that includes the pCPU
that the vCPU was last running on, the generic scheduler code would not
force a migration of that vCPU, and hence it would forever stay on the
pCPU it last ran on. Since that can again create a load imbalance, the
SEDF scheduler wants a migration to happen regardless of it being
apparently unnecessary.
Of course, an alternative to checking for SEDF explicitly in
vcpu_set_affinity() would be to introduce a flags field in struct
scheduler, and have SEDF set a "always-migrate-on-affinity-change"
flag.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
Diffstat (limited to 'xen/common/schedule.c')
-rw-r--r-- | xen/common/schedule.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/xen/common/schedule.c b/xen/common/schedule.c index 1fc9b7df6c..de111105c4 100644 --- a/xen/common/schedule.c +++ b/xen/common/schedule.c @@ -613,7 +613,8 @@ int vcpu_set_affinity(struct vcpu *v, const cpumask_t *affinity) vcpu_schedule_lock_irq(v); cpumask_copy(v->cpu_affinity, affinity); - if ( !cpumask_test_cpu(v->processor, v->cpu_affinity) ) + if ( VCPU2OP(v)->sched_id == XEN_SCHEDULER_SEDF || + !cpumask_test_cpu(v->processor, v->cpu_affinity) ) set_bit(_VPF_migrating, &v->pause_flags); vcpu_schedule_unlock_irq(v); |