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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 | |
parent | 0d460ffc0956d2dbe12ca9f5f6aa0f8701ea9d73 (diff) | |
download | kernel_goldelico_gta04-743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a.zip kernel_goldelico_gta04-743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a.tar.gz kernel_goldelico_gta04-743eeb0b01d2fbf4154bf87bff1ebb6fb18aeb7a.tar.bz2 |
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')
-rw-r--r-- | virt/kvm/coalesced_mmio.c | 3 | ||||
-rw-r--r-- | virt/kvm/eventfd.c | 3 | ||||
-rw-r--r-- | virt/kvm/ioapic.c | 3 | ||||
-rw-r--r-- | virt/kvm/kvm_main.c | 112 |
4 files changed, 106 insertions, 15 deletions
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c index 2316ec1..a6ec206 100644 --- a/virt/kvm/coalesced_mmio.c +++ b/virt/kvm/coalesced_mmio.c @@ -141,7 +141,8 @@ int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm, dev->zone = *zone; mutex_lock(&kvm->slots_lock); - ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, &dev->dev); + ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, zone->addr, + zone->size, &dev->dev); if (ret < 0) goto out_free_dev; list_add_tail(&dev->list, &kvm->coalesced_zones); diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 73358d2..f59c1e8 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -586,7 +586,8 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) kvm_iodevice_init(&p->dev, &ioeventfd_ops); - ret = kvm_io_bus_register_dev(kvm, bus_idx, &p->dev); + ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length, + &p->dev); if (ret < 0) goto unlock_fail; diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c index 8df1ca1..3eed61e 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; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index aefdda3..d9cfb78 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -47,6 +47,8 @@ #include <linux/srcu.h> #include <linux/hugetlb.h> #include <linux/slab.h> +#include <linux/sort.h> +#include <linux/bsearch.h> #include <asm/processor.h> #include <asm/io.h> @@ -2391,24 +2393,92 @@ static void kvm_io_bus_destroy(struct kvm_io_bus *bus) int i; for (i = 0; i < bus->dev_count; i++) { - struct kvm_io_device *pos = bus->devs[i]; + struct kvm_io_device *pos = bus->range[i].dev; kvm_iodevice_destructor(pos); } kfree(bus); } +int kvm_io_bus_sort_cmp(const void *p1, const void *p2) +{ + const struct kvm_io_range *r1 = p1; + const struct kvm_io_range *r2 = p2; + + if (r1->addr < r2->addr) + return -1; + if (r1->addr + r1->len > r2->addr + r2->len) + return 1; + return 0; +} + +int kvm_io_bus_insert_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev, + gpa_t addr, int len) +{ + if (bus->dev_count == NR_IOBUS_DEVS) + return -ENOSPC; + + 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; +} + +int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus, + gpa_t addr, int len) +{ + struct kvm_io_range *range, key; + int off; + + key = (struct kvm_io_range) { + .addr = addr, + .len = len, + }; + + range = bsearch(&key, bus->range, bus->dev_count, + sizeof(struct kvm_io_range), kvm_io_bus_sort_cmp); + if (range == NULL) + return -ENOENT; + + off = range - bus->range; + + while (off > 0 && kvm_io_bus_sort_cmp(&key, &bus->range[off-1]) == 0) + off--; + + return off; +} + /* kvm_io_bus_write - called under kvm->slots_lock */ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len, const void *val) { - int i; + int idx; struct kvm_io_bus *bus; + struct kvm_io_range range; + + range = (struct kvm_io_range) { + .addr = addr, + .len = len, + }; bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu); - for (i = 0; i < bus->dev_count; i++) - if (!kvm_iodevice_write(bus->devs[i], addr, len, val)) + idx = kvm_io_bus_get_first_dev(bus, addr, len); + if (idx < 0) + return -EOPNOTSUPP; + + while (idx < bus->dev_count && + kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) { + if (!kvm_iodevice_write(bus->range[idx].dev, addr, len, val)) return 0; + idx++; + } + return -EOPNOTSUPP; } @@ -2416,19 +2486,33 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len, void *val) { - int i; + int idx; struct kvm_io_bus *bus; + struct kvm_io_range range; + + range = (struct kvm_io_range) { + .addr = addr, + .len = len, + }; bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu); - for (i = 0; i < bus->dev_count; i++) - if (!kvm_iodevice_read(bus->devs[i], addr, len, val)) + idx = kvm_io_bus_get_first_dev(bus, addr, len); + if (idx < 0) + return -EOPNOTSUPP; + + while (idx < bus->dev_count && + kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) { + if (!kvm_iodevice_read(bus->range[idx].dev, addr, len, val)) return 0; + idx++; + } + return -EOPNOTSUPP; } /* Caller must hold slots_lock. */ -int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, - struct kvm_io_device *dev) +int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, + int len, struct kvm_io_device *dev) { struct kvm_io_bus *new_bus, *bus; @@ -2440,7 +2524,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, if (!new_bus) return -ENOMEM; memcpy(new_bus, bus, sizeof(struct kvm_io_bus)); - new_bus->devs[new_bus->dev_count++] = dev; + kvm_io_bus_insert_dev(new_bus, dev, addr, len); rcu_assign_pointer(kvm->buses[bus_idx], new_bus); synchronize_srcu_expedited(&kvm->srcu); kfree(bus); @@ -2464,9 +2548,13 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, r = -ENOENT; for (i = 0; i < new_bus->dev_count; i++) - if (new_bus->devs[i] == dev) { + if (new_bus->range[i].dev == dev) { r = 0; - new_bus->devs[i] = new_bus->devs[--new_bus->dev_count]; + new_bus->dev_count--; + new_bus->range[i] = new_bus->range[new_bus->dev_count]; + sort(new_bus->range, new_bus->dev_count, + sizeof(struct kvm_io_range), + kvm_io_bus_sort_cmp, NULL); break; } |