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| author | Sasha Levin <levinsasha928@gmail.com> | 2011-07-27 16:00:48 +0300 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2011-09-25 19:17:59 +0300 |
| commit | 743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a (patch) | |
| tree | 5392464930f7e77131d65f32ba96ce4665307629 /virt/kvm/ioapic.c | |
| parent | 0d460ffc0956d2dbe12ca9f5f6aa0f8701ea9d73 (diff) | |
| download | lwn-743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a.tar.gz lwn-743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a.zip | |
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')
| -rw-r--r-- | virt/kvm/ioapic.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c index 8df1ca104a7f..3eed61eb4867 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; mutex_lock(&kvm->slots_lock); - 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); mutex_unlock(&kvm->slots_lock); if (ret < 0) { kvm->arch.vioapic = NULL; |