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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 /include/linux/kvm_host.h
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 'include/linux/kvm_host.h')
-rw-r--r--include/linux/kvm_host.h18
1 files changed, 9 insertions, 9 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ff4d4062af9d..d0e42f30edf6 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -55,16 +55,16 @@ struct kvm;
struct kvm_vcpu;
extern struct kmem_cache *kvm_vcpu_cache;
-/*
- * It would be nice to use something smarter than a linear search, TBD...
- * Thankfully we dont expect many devices to register (famous last words :),
- * so until then it will suffice. At least its abstracted so we can change
- * in one place.
- */
+struct kvm_io_range {
+ gpa_t addr;
+ int len;
+ struct kvm_io_device *dev;
+};
+
struct kvm_io_bus {
int dev_count;
#define NR_IOBUS_DEVS 300
- struct kvm_io_device *devs[NR_IOBUS_DEVS];
+ struct kvm_io_range range[NR_IOBUS_DEVS];
};
enum kvm_bus {
@@ -77,8 +77,8 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
int len, const void *val);
int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len,
void *val);
-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);
int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
struct kvm_io_device *dev);