From d4c67a7a54f12cb8d267284212f1072c95917e5a Mon Sep 17 00:00:00 2001 From: Gal Hammer Date: Tue, 16 Jan 2018 15:34:41 +0200 Subject: kvm: use insert sort in kvm_io_bus_register_dev function MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Uri Lublin Signed-off-by: Gal Hammer Signed-off-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- virt/kvm/kvm_main.c | 36 ++++++++++++++++++------------------ 1 file changed, 18 insertions(+), 18 deletions(-) (limited to 'virt/kvm/kvm_main.c') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 65dea3ffef68..c7b2e927f699 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3398,21 +3398,6 @@ static int kvm_io_bus_sort_cmp(const void *p1, const void *p2) return kvm_io_bus_cmp(p1, p2); } -static int kvm_io_bus_insert_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev, - gpa_t addr, int len) -{ - bus->range[bus->dev_count++] = (struct kvm_io_range) { - .addr = addr, - .len = len, - .dev = dev, - }; - - sort(bus->range, bus->dev_count, sizeof(struct kvm_io_range), - kvm_io_bus_sort_cmp, NULL); - - return 0; -} - static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus, gpa_t addr, int len) { @@ -3553,7 +3538,9 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr, int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len, struct kvm_io_device *dev) { + int i; struct kvm_io_bus *new_bus, *bus; + struct kvm_io_range range; bus = kvm_get_bus(kvm, bus_idx); if (!bus) @@ -3567,9 +3554,22 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, sizeof(struct kvm_io_range)), GFP_KERNEL); if (!new_bus) return -ENOMEM; - memcpy(new_bus, bus, sizeof(*bus) + (bus->dev_count * - sizeof(struct kvm_io_range))); - kvm_io_bus_insert_dev(new_bus, dev, addr, len); + + range = (struct kvm_io_range) { + .addr = addr, + .len = len, + .dev = dev, + }; + + for (i = 0; i < bus->dev_count; i++) + if (kvm_io_bus_cmp(&bus->range[i], &range) > 0) + break; + + memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range)); + new_bus->dev_count++; + new_bus->range[i] = range; + memcpy(new_bus->range + i + 1, bus->range + i, + (bus->dev_count - i) * sizeof(struct kvm_io_range)); rcu_assign_pointer(kvm->buses[bus_idx], new_bus); synchronize_srcu_expedited(&kvm->srcu); kfree(bus); -- cgit v1.2.3-59-g8ed1b