Abstract: A method can include, based on a context of a wearable device, periodically capturing and storing, by the wearable device, multiple images, the multiple images being stored in a buffer included in the wearable device, periodically erasing a least-valuable image, from among the multiple images, from the buffer, receiving a request to view the multiple images stored in the buffer, and in response to the request to view the multiple images stored in the buffer, outputting the multiple images stored in the buffer.

Abstract: Provided are methods and systems for memory decompression using a hardware decompressor that minimizes or eliminates the involvement of software. Custom decompression hardware is added to the memory subsystem, where the decompression hardware handles read accesses caused by, for example, cache misses or requests from devices to compressed memory blocks, by reading a compressed block, decompressing it into an internal buffer, and returning the requested portion of the block. The custom hardware is designed to determine if the block is compressed, and determine the parameters of compression, by checking unused high bits of the physical address of the access. This allows compression to be implemented without additional metadata, because the necessary metadata can be stored in unused bits in the existing page table structures.

Abstract: Provided are methods and systems for memory decompression using a hardware decompressor that minimizes or eliminates the involvement of software. Custom decompression hardware is added to the memory subsystem, where the decompression hardware handles read accesses caused by, for example, cache misses or requests from devices to compressed memory blocks, by reading a compressed block, decompressing it into an internal buffer, and returning the requested portion of the block. The custom hardware is designed to determine if the block is compressed, and determine the parameters of compression, by checking unused high bits of the physical address of the access. This allows compression to be implemented without additional metadata, because the necessary metadata can be stored in unused bits in the existing page table structures.

Abstract: In a computer system running at least a first virtual machine (VM) and a second VM on virtualization software, a computer implemented method for the second VM to provide quasi-lockstep fault tolerance for the first VM. The method includes enabling operations of the second VM to diverge from being in lockstep with operations with the first VM without resynchronizing the second VM with the first VM, if output of the second VM is not diverging from output of the first VM. The output of the second VM is compared with the output of the first VM to determine whether the output of the second VM has diverged from the output of the first VM. In response to a determination that the output of the second VM has diverged from the output of the first VM, a resynchronization of the second VM is executed.

Abstract: A component manages and minimizes latency introduced by virtualization. The virtualization component determines that a currently scheduled guest process has executed functionality responsive to which the virtualization component is to execute a virtualization based operation, wherein the virtualization based operation is one that is not visible to the guest operating system. The virtualization component causes the guest operating system to de-schedule the currently scheduled guest process and schedule at least one separate guest process. The virtualization component then executes the virtualization based operation concurrently with the execution of the at least one separate guest process. Responsive to completing the execution of the virtualization based operation, the virtualization component causes the guest operating system to re-schedule the de-scheduled guest process.

Abstract: Replay-time-only functionalities in a computer program are executed only during replay in a virtual machine and are skipped outside of replay. If a replay-time-only functionality is detected during the replay of a program execution in a virtual machine, the replay may be paused and the virtual machine state may be saved. The replay-time-only core functionality is executed. When this execution is complete, a prior state of the virtual machine may be restored and the replay may be resumed.

Abstract: In a computer system running at least a first virtual machine (VM) and a second VM on virtualization software, a computer implemented method for the second VM to provide quasi-lockstep fault tolerance for the first VM. The method includes enabling operations of the second VM to diverge from being in lockstep with operations with the first VM without resynchronizing the second VM with the first VM, if output of the second VM is not diverging from output of the first VM. The output of the second VM is compared with the output of the first VM to determine whether the output of the second VM has diverged from the output of the first VM. In response to a determination that the output of the second VM has diverged from the output of the first VM, a resynchronization of the second VM is executed.

Abstract: In a computer system running a primary virtual machine (VM) on virtualization software on a primary virtualized computer system (VCS) and running a secondary VM on virtualization software on a secondary VCS, a method for the secondary VM to provide quasi-lockstep fault tolerance for the primary VM includes: as the primary VM is executing a workload, virtualization software in the primary VCS is: (a) causing predetermined events to be recorded in an event log, (b) keeping output associated with the predetermined events pending, and (c) sending the log entries to the virtualization software in the secondary VCS; as the secondary VM is replaying the workload, virtualization software in the secondary VCS is: (a) sending acknowledgements indicating that log entries have been received; (b) when the virtualization software encounters one of the predetermined events, searching the log entries to determine whether a log entry corresponding to the same event was received from the primary VCS, and if so, comparing data

Abstract: A method is provided for creating and maintaining the validity of a cache group including one or more cache elements. Each of the cache elements corresponds to a different address space in a virtual memory of a computer system. Each of the cache elements include one or more caches that store mappings from virtual addresses to data or values that are functions of or dependent upon physical addresses that correspond to the virtual addresses. When there is an address space switch from a first address space to a second address space, the cache group is searched to find the cache element corresponding to the second address space, and that found cache element is made the current cache element for virtual memory access through the cache element. Changes in the page tables are also detected and reflected in the caches of the cache group to maintain the caches up-to-date.

Abstract: In a computer system running a primary virtual machine (VM) on virtualization software on a primary virtualized computer system (VCS) and running a secondary VM on virtualization software on a secondary VCS, a method for the secondary VM to provide quasi-lockstep fault tolerance for the primary VM includes: as the primary VM is executing a workload, virtualization software in the primary VCS is: (a) causing predetermined events to be recorded in an event log, (b) keeping output associated with the predetermined events pending, and (c) sending the log entries to the virtualization software in the secondary VCS; as the secondary VM is replaying the workload, virtualization software in the secondary VCS is: (a) sending acknowledgements indicating that log entries have been received; (b) when the virtualization software encounters one of the predetermined events, searching the log entries to determine whether a log entry corresponding to the same event was received from the primary VCS, and if so, comparing data

Abstract: A method is provided for creating and maintaining the validity of a cache group including one or more cache elements. Each of the cache elements corresponds to a different address space in a virtual memory of a computer system. Each of the cache elements include one or more caches that store mappings from virtual addresses to data or values that are functions of or dependent upon physical addresses that correspond to the virtual addresses. When there is an address space switch from a first address space to a second address space, the cache group is searched to find the cache element corresponding to the second address space, and that found cache element is made the current cache element for virtual memory access through the cache element. Changes in the page tables are also detected and reflected in the caches of the cache group to maintain the caches up-to-date.

Abstract: A component manages and minimizes latency introduced by virtualization. The virtualization component determines that a currently scheduled guest process has executed functionality responsive to which the virtualization component is to execute a virtualization based operation, wherein the virtualization based operation is one that is not visible to the guest operating system. The virtualization component causes the guest operating system to de-schedule the currently scheduled guest process and schedule at least one separate guest process. The virtualization component then executes the virtualization based operation concurrently with the execution of the at least one separate guest process. Responsive to completing the execution of the virtualization based operation, the virtualization component causes the guest operating system to re-schedule the de-scheduled guest process.

Abstract: Replay-time-only functionalities in a computer program are executed only during replay in a virtual machine and are skipped outside of replay. If a replay-time-only functionality is detected during the replay of a program execution in a virtual machine, the replay may be paused and the virtual machine state may be saved. The replay-time-only core functionality is executed. When this execution is complete, a prior state of the virtual machine may be restored and the replay may be resumed.