path: root/virt/kvm/ioapic.c
diff options
authorSasha Levin <levinsasha928@gmail.com>2011-07-27 16:00:48 +0300
committerAvi Kivity <avi@redhat.com>2011-09-25 19:17:59 +0300
commit743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a (patch)
tree5392464930f7e77131d65f32ba96ce4665307629 /virt/kvm/ioapic.c
parent0d460ffc0956d2dbe12ca9f5f6aa0f8701ea9d73 (diff)
KVM: Intelligent device lookup on I/O bus
Currently the method of dealing with an IO operation on a bus (PIO/MMIO) is to call the read or write callback for each device registered on the bus until we find a device which handles it. Since the number of devices on a bus can be significant due to ioeventfds and coalesced MMIO zones, this leads to a lot of overhead on each IO operation. Instead of registering devices, we now register ranges which points to a device. Lookup is done using an efficient bsearch instead of a linear search. Performance test was conducted by comparing exit count per second with 200 ioeventfds created on one byte and the guest is trying to access a different byte continuously (triggering usermode exits). Before the patch the guest has achieved 259k exits per second, after the patch the guest does 274k exits per second. Cc: Avi Kivity <avi@redhat.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'virt/kvm/ioapic.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 8df1ca104a7..3eed61eb486 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -394,7 +394,8 @@ int kvm_ioapic_init(struct kvm *kvm)
kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
ioapic->kvm = kvm;
- ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, &ioapic->dev);
+ ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, ioapic->base_address,
+ IOAPIC_MEM_LENGTH, &ioapic->dev);
if (ret < 0) {
kvm->arch.vioapic = NULL;