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Date: Wed, 27 Oct 2010 17:09:41 +0800
From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To: Avi Kivity <avi@...hat.com>
CC: Marcelo Tosatti <mtosatti@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: [PATCH 7/8] KVM: make async_pf work queue lockless
The async_pf number is very few since only pending interrupt can
let it re-enter to the guest mode.
During my test(Host 4 CPU + 4G, Guest 4 VCPU + 6G), it's no
more than 10 requests in the system.
So, we can only increase the completion counter in the work queue
context, and walk vcpu->async_pf.queue list to get all completed
async_pf
Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
include/linux/kvm_host.h | 4 +--
virt/kvm/async_pf.c | 50 +++++++++++++++++++--------------------------
2 files changed, 22 insertions(+), 32 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d91add9..33c03c3 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -78,7 +78,6 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
#ifdef CONFIG_KVM_ASYNC_PF
struct kvm_async_pf {
struct work_struct work;
- struct list_head link;
struct list_head queue;
struct kvm_vcpu *vcpu;
struct mm_struct *mm;
@@ -127,10 +126,9 @@ struct kvm_vcpu {
#ifdef CONFIG_KVM_ASYNC_PF
struct {
+ atomic_t done;
u32 queued;
struct list_head queue;
- struct list_head done;
- spinlock_t lock;
bool wakeup;
} async_pf;
#endif
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 0d1f6c4..f10de1e 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -49,9 +49,7 @@ void kvm_async_pf_deinit(void)
void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
{
- INIT_LIST_HEAD(&vcpu->async_pf.done);
INIT_LIST_HEAD(&vcpu->async_pf.queue);
- spin_lock_init(&vcpu->async_pf.lock);
}
static void async_pf_execute(struct work_struct *work)
@@ -72,11 +70,9 @@ static void async_pf_execute(struct work_struct *work)
up_read(&mm->mmap_sem);
unuse_mm(mm);
- spin_lock(&vcpu->async_pf.lock);
- list_add_tail(&apf->link, &vcpu->async_pf.done);
apf->page = page;
apf->done = true;
- spin_unlock(&vcpu->async_pf.lock);
+ atomic_inc(&vcpu->async_pf.done);
/*
* apf may be freed by kvm_check_async_pf_completion() after
@@ -101,52 +97,48 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
typeof(*work), queue);
cancel_work_sync(&work->work);
list_del(&work->queue);
- if (!work->done) /* work was canceled */
- kmem_cache_free(async_pf_cache, work);
- }
-
- spin_lock(&vcpu->async_pf.lock);
- while (!list_empty(&vcpu->async_pf.done)) {
- struct kvm_async_pf *work =
- list_entry(vcpu->async_pf.done.next,
- typeof(*work), link);
- list_del(&work->link);
if (work->page)
put_page(work->page);
kmem_cache_free(async_pf_cache, work);
}
- spin_unlock(&vcpu->async_pf.lock);
vcpu->async_pf.queued = 0;
+ atomic_set(&vcpu->async_pf.done, 0);
}
bool kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
{
struct kvm_async_pf *work;
+ struct list_head *pos, *temp;
if (vcpu->async_pf.wakeup) {
vcpu->async_pf.wakeup = false;
return true;
}
- if (list_empty_careful(&vcpu->async_pf.done) ||
+ if (!atomic_read(&vcpu->async_pf.done) ||
!kvm_arch_can_inject_async_page_present(vcpu))
return false;
- spin_lock(&vcpu->async_pf.lock);
- work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
- list_del(&work->link);
- spin_unlock(&vcpu->async_pf.lock);
+ list_for_each_safe(pos, temp, &vcpu->async_pf.queue) {
+ work = list_entry(pos, typeof(*work), queue);
+ if (!work->done)
+ continue;
- if (work->page)
- kvm_arch_async_page_ready(vcpu, work);
- kvm_arch_async_page_present(vcpu, work);
+ if (work->page) {
+ kvm_arch_async_page_ready(vcpu, work);
+ put_page(work->page);
+ }
+
+ kvm_arch_async_page_present(vcpu, work);
+
+ list_del(&work->queue);
+ vcpu->async_pf.queued--;
+ kmem_cache_free(async_pf_cache, work);
+ if (atomic_dec_and_test(&vcpu->async_pf.done))
+ break;
+ }
- list_del(&work->queue);
- vcpu->async_pf.queued--;
- if (work->page)
- put_page(work->page);
- kmem_cache_free(async_pf_cache, work);
kvm_arch_async_pf_completion(vcpu);
return true;
--
1.7.0.4
--
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