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KVM: Remove deprecated create_singlethread_workqueue

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The workqueue "irqfd_cleanup_wq" queues a single work item
&irqfd->shutdown and hence doesn't require ordering. It is a host-wide
workqueue for issuing deferred shutdown requests aggregated from all
vm* instances. It is not being used on a memory reclaim path.
Hence, it has been converted to use system_wq.
The work item has been flushed in kvm_irqfd_release().

The workqueue "wqueue" queues a single work item &timer->expired
and hence doesn't require ordering. Also, it is not being used on
a memory reclaim path. Hence, it has been converted to use system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Bhaktipriya Shridhar 2016-08-30 23:29:51 +05:30 committed by Paolo Bonzini
parent f15a75eedc
commit 3706feacd0
3 changed files with 5 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
virt/kvm/arm/arch_timer.c
View File

@ -31,7 +31,6 @@
#include "trace.h"
static struct timecounter *timecounter;
static struct workqueue_struct *wqueue;
static unsigned int host_vtimer_irq;
static u32 host_vtimer_irq_flags;
@ -141,7 +140,7 @@ static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
return HRTIMER_RESTART;
}
queue_work(wqueue, &timer->expired);
schedule_work(&timer->expired);
return HRTIMER_NORESTART;
}
@ -449,12 +448,6 @@ int kvm_timer_hyp_init(void)
goto out;
}
wqueue = create_singlethread_workqueue("kvm_arch_timer");
if (!wqueue) {
err = -ENOMEM;
goto out_free;
}
kvm_info("virtual timer IRQ%d\n", host_vtimer_irq);
cpuhp_setup_state(CPUHP_AP_KVM_ARM_TIMER_STARTING,
@ -518,7 +511,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
* VCPUs have the enabled variable set, before entering the guest, if
* the arch timers are enabled.
*/
if (timecounter && wqueue)
if (timecounter)
timer->enabled = 1;
return 0;

22
virt/kvm/eventfd.c
View File

@ -42,7 +42,6 @@
#ifdef CONFIG_HAVE_KVM_IRQFD
static struct workqueue_struct *irqfd_cleanup_wq;
static void
irqfd_inject(struct work_struct *work)
@ -168,7 +167,7 @@ irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
list_del_init(&irqfd->list);
queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
schedule_work(&irqfd->shutdown);
}
int __attribute__((weak)) kvm_arch_set_irq_inatomic(
@ -555,7 +554,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
* so that we guarantee there will not be any more interrupts on this
* gsi once this deassign function returns.
*/
flush_workqueue(irqfd_cleanup_wq);
flush_work(&irqfd->shutdown);
return 0;
}
@ -592,7 +591,7 @@ kvm_irqfd_release(struct kvm *kvm)
* Block until we know all outstanding shutdown jobs have completed
* since we do not take a kvm* reference.
*/
flush_workqueue(irqfd_cleanup_wq);
flush_work(&irqfd->shutdown);
}
@ -622,23 +621,8 @@ void kvm_irq_routing_update(struct kvm *kvm)
spin_unlock_irq(&kvm->irqfds.lock);
}
/*
* create a host-wide workqueue for issuing deferred shutdown requests
* aggregated from all vm* instances. We need our own isolated single-thread
* queue to prevent deadlock against flushing the normal work-queue.
*/
int kvm_irqfd_init(void)
{
irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
if (!irqfd_cleanup_wq)
return -ENOMEM;
return 0;
}
void kvm_irqfd_exit(void)
{
destroy_workqueue(irqfd_cleanup_wq);
}
#endif

6
virt/kvm/kvm_main.c
View File

@ -3807,12 +3807,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
* kvm_arch_init makes sure there's at most one caller
* for architectures that support multiple implementations,
* like intel and amd on x86.
* kvm_arch_init must be called before kvm_irqfd_init to avoid creating
* conflicts in case kvm is already setup for another implementation.
*/
r = kvm_irqfd_init();
if (r)
goto out_irqfd;
if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
r = -ENOMEM;
@ -3894,7 +3889,6 @@ out_free_0a:
free_cpumask_var(cpus_hardware_enabled);
out_free_0:
kvm_irqfd_exit();
out_irqfd:
kvm_arch_exit();
out_fail:
return r;