Now, we have 'vcpu->guest_mode' to judge whether need to send
ipi to other cpus, this way is very exact, so checking request
bit is needless, then we can drop the spinlock let it's collateral
There is the simple test result of kernbench:
before patch:
real 5m5.100s
user 3m58.051s
sys 9m4.742s
real 5m3.443s
user 3m58.837s
sys 9m6.007s
after patch:
real 5m0.769s
user 3m59.666s
sys 8m41.406s
real 4m57.980s
user 3m59.302s
sys 8m38.916s
Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
---
include/linux/kvm_host.h | 6 ------
virt/kvm/kvm_main.c | 9 +++------
2 files changed, 3 insertions(+), 12 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b5021db..3e64133 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -212,7 +212,6 @@ struct kvm_memslots {
struct kvm {
spinlock_t mmu_lock;
- raw_spinlock_t requests_lock;
struct mutex slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
struct kvm_memslots *memslots;
@@ -719,11 +718,6 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
set_bit(req, &vcpu->requests);
}
-static inline bool kvm_make_check_request(int req, struct kvm_vcpu *vcpu)
-{
- return test_and_set_bit(req, &vcpu->requests);
-}
-
static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
{
if (test_bit(req, &vcpu->requests)) {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6648c6e..34066ab 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -147,11 +147,9 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
zalloc_cpumask_var(&cpus, GFP_ATOMIC);
- raw_spin_lock(&kvm->requests_lock);
- me = smp_processor_id();
+ me = get_cpu();
kvm_for_each_vcpu(i, vcpu, kvm) {
- if (kvm_make_check_request(req, vcpu))
- continue;
+ kvm_make_request(req, vcpu);
cpu = vcpu->cpu;
if (cpus != NULL && cpu != -1 && cpu != me &&
atomic_read(&vcpu->guest_mode))
@@ -163,7 +161,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
smp_call_function_many(cpus, ack_flush, NULL, 1);
else
called = false;
- raw_spin_unlock(&kvm->requests_lock);
+ put_cpu();
free_cpumask_var(cpus);
return called;
}
@@ -429,7 +427,6 @@ static struct kvm *kvm_create_vm(void)
kvm->mm = current->mm;
atomic_inc(&kvm->mm->mm_count);
spin_lock_init(&kvm->mmu_lock);
- raw_spin_lock_init(&kvm->requests_lock);
kvm_eventfd_init(kvm);
mutex_init(&kvm->lock);
mutex_init(&kvm->irq_lock);
--
1.7.3.4
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
