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kvm: use insert sort in kvm_io_bus_register_dev function
The loading time of a VM is quite significant with a CPU usage reaching 100% when loading a VM that its virtio devices use a large amount of virt-queues (e.g. a virtio-serial device with max_ports=511). Most of the time is spend in re-sorting the kvm_io_bus kvm_io_range array when a new eventfd is registered. The patch replaces the existing method with an insert sort. Reviewed-by: Marcel Apfelbaum <marcel@redhat.com> Reviewed-by: Uri Lublin <ulublin@redhat.com> Signed-off-by: Gal Hammer <ghammer@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
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@ -3398,21 +3398,6 @@ static int kvm_io_bus_sort_cmp(const void *p1, const void *p2)
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return kvm_io_bus_cmp(p1, p2);
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}
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static int kvm_io_bus_insert_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev,
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gpa_t addr, int len)
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{
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bus->range[bus->dev_count++] = (struct kvm_io_range) {
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.addr = addr,
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.len = len,
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.dev = dev,
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};
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sort(bus->range, bus->dev_count, sizeof(struct kvm_io_range),
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kvm_io_bus_sort_cmp, NULL);
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return 0;
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}
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static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus,
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gpa_t addr, int len)
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{
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@ -3553,7 +3538,9 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
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int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
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int len, struct kvm_io_device *dev)
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{
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int i;
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struct kvm_io_bus *new_bus, *bus;
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struct kvm_io_range range;
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bus = kvm_get_bus(kvm, bus_idx);
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if (!bus)
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@ -3567,9 +3554,22 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
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sizeof(struct kvm_io_range)), GFP_KERNEL);
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if (!new_bus)
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return -ENOMEM;
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memcpy(new_bus, bus, sizeof(*bus) + (bus->dev_count *
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sizeof(struct kvm_io_range)));
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kvm_io_bus_insert_dev(new_bus, dev, addr, len);
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range = (struct kvm_io_range) {
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.addr = addr,
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.len = len,
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.dev = dev,
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};
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for (i = 0; i < bus->dev_count; i++)
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if (kvm_io_bus_cmp(&bus->range[i], &range) > 0)
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break;
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memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
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new_bus->dev_count++;
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new_bus->range[i] = range;
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memcpy(new_bus->range + i + 1, bus->range + i,
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(bus->dev_count - i) * sizeof(struct kvm_io_range));
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rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
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synchronize_srcu_expedited(&kvm->srcu);
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kfree(bus);
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