Digital Equipment Corporation

Microsoft Technology Licensing, LLC

David N Cutler

Richard T Witek

David A Orbits

Wayne M Cardoza

Dileep P Bhandarkar

James W Kelly

Frank L Perazzoli, Sr

Robert T Short

Thomas Fahrig

H Bruce Butts, Jr

Peter C Schnorr

Mark H Lucovsky

Forrest Curtis Foltz

John D Vert

Darryl E Havens

Theodore H Kehl

Steven R Wood

Scott Field

Eric P Traut

Gopala Krishna R Kakivaya

John M Parchem

Robert E Stewart

James M Lyon

Mark James McNulty

Brandon S Baker

Suyash Sinha

Charles T Lenzmeier

Scott D Mosier

James J Radigan

Ian H Carmichael

Judson S Leonard

Lawrence B Sullivan

Thomas R Ermolovich

Joy Ganguly

Blaine Craig Hauglie

Paul Joseph Wolfteich

The present disclosure relates to devices, methods, and computer-readable medium for saving and restoring physical hardware states and virtual machine (VM) states for an application actively being executed on a virtual machine by a user on a computer device. The devices, methods, and computer-readable medium may allow a user to suspend a current state of an application session and save the VM and memory state to persistent storage, and later resume the execution of the saved application session by reading the state back into memory and restoring the VM state.

Saving and restoring virtual machine states and hardware states for application content

Computerized methods, computer systems, and computer-readable media for governing how virtual processors are scheduled to particular logical processors are provided. A scheduler is employed to balance a load imposed by virtual machines, each having a plurality of virtual processors, across various logical processors (comprising a physical machine) that are running threads in parallel. The threads are issued by the virtual processors and often cause spin waits that inefficiently consume capacity of the logical processors that are executing the threads. Upon detecting a spin-wait state of the logical processor(s), the scheduler will opportunistically grant time-slice extensions to virtual processors that are running a critical section of code, thus, mitigating performance loss on the front end. Also, the scheduler will mitigate performance loss on the back end by opportunistically de-scheduling then rescheduling a virtual machine in a spin-wait state to render the logical processor(s) available for other work in the interim.

Opportunistically scheduling and adjusting time slices

Page tables in the last level of a hierarchical page table system are scanned for candidate page tables. Candidate page tables are converted to large pages, having a page table entry in a level before the last level of the hierarchical page table system adjusted to be associated with the newly created large page. Upon receiving a notification that a large page is to be converted into a page table, a new page table is created. Each entry in the new page table is associated with a small segment of memory in the large page and an entry in a page table one level before the last level in a hierarchical page table system is adjusted to be associated with the new page table.

Opportunistic page largification

This document describes tools capable of enabling a protection agent to determine, from memory inaccessible from an operating-system privilege mode, whether one or more resources of an operating system have been modified. In some instances, these tools may enable the protection agent to reside within a virtual machine monitor. In other instances, the tools may enable the protection agent to reside within a distinct virtual partition provided by the virtual machine monitor. By operating outside of the operating-system privilege mode, the protection agent may be less vulnerable to attacks by entities operating within the operating-system privilege mode.

Protecting operating-system resources

In an exemplary media implementation, one or more electronically-accessible media include electronically-executable instructions that utilize an application programming interface, the application programming interface facilitating creation of callback-type dynamic function tables; each callback-type dynamic function table including a begin address, an end address, and a callback function, each callback-type dynamic function table corresponding to a code heap that stores code for multiple functions in a runtime environment; wherein interaction between the runtime environment and an operating system is precipitated upon calling the callback function to acquire exception handling and/or unwind information. In another exemplary media implementation, one or more electronically-accessible media include at least part of an operating system that is configured to request from a runtime environment exception handling and/or unwinding information for functions that are managed by the runtime environment.

Operating system managing a linked list of callback dynamic function tables for acquiring exception handling information from a runtime environment

Synchronization services provide a concurrency-safe reader/writer lock supporting a time out feature. The lock can be implemented using lockless data structures to provide efficient synchronization services. Various features such as lock nesting and auto-transformation address common scenarios arising in componentized programs. The lock supports upgrading and suspension, and the time out feature can support an efficient, low-cost optimistic deadlock avoidance scheme. Peculiarities of the reader/writer scenario are addressed in an efficient way to maintain lock stability and consistency, thus providing synchronization services suitable for implementation at the kernel level. In one implementation using event objects, the events are managed for high efficiency and stability of the lock. For multiprocessor machines, a hybrid lock avoids a context switch by behaving as a spin lock before waiting for the lock to become available.

Concurrency-safe reader-writer lock with time out support

A technique for performing multiple simultaneous asynchronous input/output operations in a computer operating system. An input/output completion port object is created and associated with a file descriptor. When I/O services are requested on the file descriptor, completion is indicated by a message queued to the I/O completion port. A process requesting I/O services is not notified of completion of the I/O services, but instead checks the I/O completion port's queue to determine the status of its I/O requests. The I/O completion port manages multiple threads and their concurrency.

Input/output completion port queue data structures and methods for using same

System for performing asynchronous file operations requested by runnable

A method and system for scheduling the execution of a plurality of threads in a computer system to control the concurrency level. Operating system data structures, called 'queue objects,' control the number of threads that are concurrently active processing incoming requests to an application program, a server or other processor of requests. The queue objects keep track of how many threads are currently active, and ensure that the number of active threads is at or near a predetermined target level of concurrency. By ensuring that new threads are not added to the pool of active threads if the system is operating at or above the target level of concurrency, the queue objects minimize the number of superfluous context switches that the operating system must perform and thus increases system efficiency and throughput.

Queue object for controlling concurrency in a computer system

A peripheral device interrupt controller maintains a count of pending interrupt events for a peripheral device up to a preset limit and times a preset delay interval from a first pending interrupt event or last interrupt servicing before asserting an interrupt request. When the interrupt request is asserted, the then pending interrupt events can be serviced as a group by a central processing unit of a computer. The overhead of processing a separate interrupt request for each interrupt event is thus avoided. The preset limit and preset delay interval can be set under software control to control the rate at which interrupt requests can be asserted by the peripheral device.

Method and apparatus for reducing the rate of interrupts by generating a

An object based operating system for a multitasking computer system provides objects which represent the architecture or interrelationships of the system's resources. Access to certain objects is required in order to use corresponding resources in the system. All objects have a consistent data structure, and a consistent method of defining the operations which apply to each type of object. As a result, it is relatively easy to add new types of system objects to the operating system. Waitable objects are used to synchronize the operation of one or more processes with one another or with specified events. The system provides routines for generating new types of waitable objects, and thereby generating a modified operating system, without modifying other aspects of the operating system's kernel.

System and method for adding new waitable object types to object

An instruction eases exception handling in a data processing system having one or more parallel pipelined execution units by permitting the central processing unit to complete instructions currently being processed by the execution units, but preventing further instructions from being initiated until all currently executing instructions have been completed and all outstanding exception conditions have been resolved. After all the instructions preceding the DRAIN instruction of the present invention in the program instruction sequence have been executed, the central processing unit can continue to execute the sequential program instructions when no arithmetic exception has been identified, or can invoke an exception handling procedure when an arithmetic exception has been identified. The instruction is typically positioned in an instruction sequence after an instruction that has high degree of probability of resulting in the identification of an arithmetic exception condition. The DRAIN instruction permits the source of the exception to be localized and permits the response to all arithmetic exceptions associated with instructions initiated before the DRAIN instruction, but identified after the execution of the DRAIN instruction, to be handled in the same context environment in which the instruction was initiated.

Method for synchronization of arithmetic exceptions in central

In a data processing system, apparatus and method for controlling the type of processing to which data signal groups can be subjected includes a page table entry format having a multiplicity of field positions for storing signals defining page access rights. In addition to the read/write access control, the signal group access rights can be determined by the current mode of operation of the data processing unit and the intended activity of the addressed instruction or data element (i.e., read, write or execute).

Apparatus and method for main memory unit protection using access and

An object based operating system for a multitasking computer system provides objects which represent the architecture or interrelationships of the system's resources. Access to certain objects is required in order to use corresponding resources in the system. All objects have a consistent data structure, and a consistent method of defining the operations which apply to each type of object. As a result, it is relatively easy to add new types of system objects to the operating system. The object based operating system supports multiple levels of visibility, allowing objects to be operated on only by processes with the object's range of visibility. This allows objects to be made private to a process, shared by all processes within a job, or visible to all processes within the system. An object or an entire set of objects can be moved to a higher visibility level when objects need to be shared. In addition, access to each object is controlled through an access control list which specifies the processes authorized to access the object, and the types of access that are allowed. An object with a restricted access control list can be associated with a 'privileged operation', thereby restricting use of the privileged operation to those user processes authorized to access the corresponding object. Waitable objects are used to synchronize the operation of one or more processes with one another or with specified events. The system provides routines for generating new types of waitable objects without modifying the operating system's kernel.

Object transferring system and method in an object based computer

Growing community of inventors

Bellevue, WA, United States of America

David N Cutler