Abstract: A storage subsystem combining solid state drive (SSD) and hard disk drive (HDD) technologies provides low access latency and low complexity. Separate free lists are maintained for the SSD and the HDD and blocks of file system data are stored uniquely on either the SSD or the HDD. When a read access is made to the subsystem, if the data is present on the SSD, the data is returned, but if the block is present on the HDD, it is migrated to the SSD and the block on the HDD is returned to the HDD free list. On a write access, if the block is present in the either the SSD or HDD, the block is overwritten, but if the block is not present in the subsystem, the block is written to the HDD.

Abstract: According to one aspect of the present disclosure, a method and technique for variable cache line size management is disclosed. The method includes: determining whether an eviction of a cache line from an upper level sectored cache to an unsectored lower level cache is to be performed, wherein the upper level cache includes a plurality of sub-sectors, each sub-sector having a cache line size corresponding to a cache line size of the lower level cache; responsive to determining that an eviction is to be performed, identifying referenced sub-sectors of the cache line to be evicted; invalidating unreferenced sub-sectors of the cache line to be evicted; and storing the referenced sub-sectors in the lower level cache.

Abstract: According to one aspect of the present disclosure, a system and technique for variable cache line size management is disclosed. The system includes a processor and a cache hierarchy, where the cache hierarchy includes a sectored upper level cache and an unsectored lower level cache, and wherein the upper level cache includes a plurality of sub-sectors, each sub-sector having a cache line size corresponding to a cache line size of the lower level cache. The system also includes logic executable to, responsive to determining that a cache line from the upper level cache is to be evicted to the lower level cache: identify referenced sub-sectors of the cache line to be evicted; invalidate unreferenced sub-sectors of the cache line to be evicted; and store the referenced sub-sectors in the lower level cache.

Abstract: A mechanism is provided for offloading an input/output (I/O) completion operation. Responsive to a second processor identifying that a flag has been set by a first processor requesting assistance in completing an I/O operation, the second processor copies an I/O response from a first I/O response data structure associated with the first processor to a second I/O response data structure associated with the second processor. The second processor deletes the I/O response from the first I/O response data structure, clears the flag, and processes the I/O operation by addressing the I/O response in the second I/O response data structure. Responsive to completing the I/O operation, the second processor deletes the I/O response from the second I/O response data structure.

Abstract: A mechanism is provided for offloading an input/output (I/O) completion operation. Responsive to a second processor identifying that a flag has been set by a first processor requesting assistance in completing an I/O operation, the second processor copies an I/O response from a first I/O response data structure associated with the first processor to a second I/O response data structure associated with the second processor. The second processor deletes the I/O response from the first I/O response data structure, clears the flag, and processes the I/O operation by addressing the I/O response in the second I/O response data structure. Responsive to completing the I/O operation, the second processor deletes the I/O response from the second I/O response data structure.

Abstract: Some embodiments of the inventive subject matter are directed to operations that include determining that an access request to a computer memory results in a cache miss. In some examples, the operations further include determining an amount of cache resources used to service additional cache misses that occurred within a period prior to the cache miss. Furthermore, in some examples, the operations further include servicing the access request to the computer memory based, at least in part, on the amount of the cache resources used to service the additional cache misses within the period prior to the cache miss.

Abstract: In a NUMA-topology computer system that includes multiple nodes and multiple logical partitions, some of which may be dedicated and others of which are shared, NUMA optimizations are enabled in shared logical partitions. This is done by specifying a home node parameter in each virtual processor assigned to a logical partition. When a task is created by an operating system in a shared logical partition, a home node is assigned to the task, and the operating system attempts to assign the task to a virtual processor that has a home node that matches the home node for the task. The partition manager then attempts to assign virtual processors to their corresponding home nodes. If this can be done, NUMA optimizations may be performed without the risk of reducing the performance of the shared logical partition.

Abstract: Some embodiments of the inventive subject matter are directed to determining that a memory access request results in a cache miss and determining an amount of cache resources used to service cache misses within a past period in response to determining that the memory access request results in the cache miss. Some embodiments are further directed to determining that servicing the memory access request would increase the amount of cache resources used to service cache misses within the past period to exceed a threshold. In some embodiments, the threshold corresponds to reservation of a given amount of cache resources for potential cache hits. Some embodiments are further directed to rejecting the memory access request in response to the determining that servicing the memory access request would increase the amount of cache resources used to service cache misses within the past period to exceed the threshold.

Abstract: Some embodiments of the inventive subject matter are directed to a cache comprising a tracking unit and cache state machines. In some embodiments, the tracking unit is configured to track an amount of cache resources used to service cache misses within a past period. In some embodiments, each of the cache state machines is configured to, determine whether a memory access request results in a cache miss or cache hit, and in response to a cache miss for a memory access request, query the tracking unit for the amount of cache resources used to service cache misses within the past period. In some embodiments, the each of the cache state machines is configured to service the memory access request based, at least in part, on the amount of cache resources used to service the cache misses within the past period according to the tracking unit.

Abstract: According to one aspect of the present disclosure, a method and technique for hybrid virtual machine configuration management is disclosed. The method includes: assigning to a first set of virtual resources associated with entitled resources of a virtual machine a first priority; assigning to a second set of virtual resources associated with the virtual machine a second priority lower than the first priority, wherein the first and seconds sets when combined exceed the entitled resources for the virtual machine; mapping the first set of virtual resources to a first physical resource of a pool of shared physical resources allocatable to the first and second sets of virtual resources, wherein the first physical resource comprises a desired affinity level to a second physical resource allocated to the virtual machine; and preferentially allocating the first physical resource to the first set of virtual resources.

Abstract: A system and technique for hybrid virtual machine configuration management includes a processor and executable logic to: assign to a first set of virtual resources associated with a virtual machine a first priority, the first set associated with entitled resources for the virtual machine; assign to a second set of virtual resources associated with the virtual machine a second priority lower than the first priority, wherein the first and seconds sets when combined exceed the entitled resources for the virtual machine; map the first set to a first physical resource of a pool of shared physical resources, the pool of shared physical resources allocatable to the first and second sets, wherein the first physical resource comprises a desired affinity level to a second physical resource allocated to the virtual machine; and preferentially allocate the first physical resource to the first set of virtual resources.

Abstract: A mechanism is provided for offloading an input/output (I/O) completion operation. Responsive to a second processor identifying that a flag has been set by a first processor requesting assistance in completing an I/O operation, the second processor copies an I/O response from a first I/O response data structure associated with the first processor to a second I/O response data structure associated with the second processor. The second processor deletes the I/O response from the first I/O response data structure, clears the flag, and processes the I/O operation by addressing the I/O response in the second I/O response data structure. Responsive to completing the I/O operation, the second processor deletes the I/O response from the second I/O response data structure.

Abstract: A mechanism is provided for offloading an input/output (I/O) completion operation. Responsive to a second processor identifying that a flag has been set by a first processor requesting assistance in completing an I/O operation, the second processor copies an I/O response from a first I/O response data structure associated with the first processor to a second I/O response data structure associated with the second processor. The second processor deletes the I/O response from the first I/O response data structure, clears the flag, and processes the I/O operation by addressing the I/O response in the second I/O response data structure. Responsive to completing the I/O operation, the second processor deletes the I/O response from the second I/O response data structure.

Abstract: Functionality is implemented to determine that a plurality of multi-core processing units of a system are configured in accordance with a plurality of operating performance modes. It is determined that a first of the plurality of operating performance modes satisfies a first performance criterion that corresponds to a first workload of a first logical partition of the system. Accordingly, the first logical partition is associated with a first set of the plurality of multi-core processing units that are configured in accordance with the first operating performance mode. It is determined that a second of the plurality of operating performance modes satisfies a second performance criterion that corresponds to a second workload of a second logical partition of the system. Accordingly, the second logical partition is associated with a second set of the plurality of multi-core processing units that are configured in accordance with the second operating performance mode.

Abstract: According to one aspect of the present disclosure a system and technique for performance-driven cache line memory access is disclosed. The system includes: a processor, a cache hierarchy coupled to the processor, and a memory coupled to the cache hierarchy. The system also includes logic executable to, responsive to receiving a request for a cache line: divide the request into a plurality of cache subline requests, wherein at least one of the cache subline requests comprises a high priority data request and at least one of the cache subline requests comprises a low priority data request; service the high priority data request; and delay servicing of the low priority data request until a low priority condition has been satisfied.

Abstract: Functionality is implemented to determine that a plurality of multi-core processing units of a system are configured in accordance with a plurality of operating performance modes. It is determined that a first of the plurality of operating performance modes satisfies a first performance criterion that corresponds to a first workload of a first logical partition of the system. Accordingly, the first logical partition is associated with a first set of the plurality of multi-core processing units that are configured in accordance with the first operating performance mode. It is determined that a second of the plurality of operating performance modes satisfies a second performance criterion that corresponds to a second workload of a second logical partition of the system. Accordingly, the second logical partition is associated with a second set of the plurality of multi-core processing units that are configured in accordance with the second operating performance mode.

Abstract: According to one aspect of the present disclosure, a method and technique for using processor registers for extending a cache structure is disclosed. The method includes identifying a register of a processor, identifying a cache to extend, allocating the register as an extension of the cache, and setting an address of the register as corresponding to an address space in the cache.

Abstract: A computer program product for scheduling threads in a multiprocessor computer comprises computer program instructions configured to select a thread in a ready queue to be dispatched to a processor and determine whether an interrupt mask flag is set in a thread control block associated with the thread. If the interrupt mask flag is set in the thread control block associated with the thread, the computer program instructions are configured to select a processor, set a current processor priority register of the selected processor to least favored, and dispatch the thread from the ready queue to the selected processor.

Abstract: A first collection of threads which represent a collection of tasks to be executed by at least one of a collection of processing units is monitored. In response to detecting a request by a thread among the first collection of threads to access a shared resource locked by a second thread among the collection of threads, the first thread attempts to access a list associated with the shared resource. The list orders at least one thread among the collection of threads by priority of access to the shared resource. In response to determining the list is locked by a third thread among the collection of threads, the first thread is placed into a sleep state to be reawakened in a fixed period of time. In response to determining that at least one of the collection of processing units has entered into an idle state, the first thread is awakened from the sleep state before the fixed period of time has expired.

Abstract: A system and technique for managing rollback in a transactional memory environment is disclosed. The system includes a processor, a transactional memory, and a transactional memory manager (TMM) configured to perform a rollback on the transactional memory. The TMM is configured to, responsive to detecting a begin transaction directive by the processor, detect an access of a first memory location of the transactional memory not needing rollback and indicate that the first memory location does not need to be rolled back while detecting an access to a second memory location of the transactional memory and indicating that a rollback will be required. The TMM is also configured to, responsive to detecting an end transaction directive after the begin transaction directive and a conflict requiring a rollback, omit a rollback of the first memory location while performing rollback on the second memory location.