Abstract: Provided are a computer program product, system, and method for determining server write activity levels to use to adjust write cache size. Information on server write activity to the cache is gathered. The gathered information on write activity is processed to determine a server write activity level comprising one of multiple write activity levels indicating a level of write activity. The determined server write activity level is transmitted to a storage server having a write cache, wherein the storage server uses the determined server write activity level to determine whether to adjust a size of the storage server write cache.

Abstract: Provided are a computer program product, system, and method for determining server write activity levels to use to adjust write cache size. Server write activity information on server write activity to the cache is gathered. The server write activity information is processed to determine a server write activity level comprising one of multiple write activity levels indicating a level of write activity. The determined server write activity level is transmitted to a storage server having a write cache, wherein the storage server uses the determined server write activity level to determine whether to adjust a size of the storage server write cache.

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 managing memory access is disclosed. The method includes setting a memory databus utilization threshold for each of a plurality of processors of a data processing system to maintain memory databus utilization of the data processing system at or below a system threshold. The method also includes monitoring memory databus utilization for the plurality of processors and, in response to determining that memory databus utilization for at least one of the processors is below its threshold, reallocating at least a portion of unused databus utilization from the at least one processor to at least one of the other processors.

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: According to one aspect of the present disclosure a system and computer program product for managing memory access is disclosed. The system includes a plurality of memory controllers each configured to maintain memory databus utilization by a corresponding processor at or below a threshold to maintain memory databus utilization of the system at or below a system threshold. The system also includes a service processor configured to receive memory databus utilization data from the memory controllers and programmed to, in response to determining that memory databus utilization for at least one of the processors is below its threshold, reallocate at least a portion of unused databus utilization from the at least one processor to at least one of the other processors.

Abstract: A method, system and program are provided for dynamically assigning priority values to instruction threads in a computer system based on one or more predetermined thread performance tests, and using the assigned instruction priorities to determine how resources are used in the system. By storing the assigning priority values for each thread as a tag in the thread's instructions, tagged instructions from different threads that are dispatched through the system are allocated system resources based on the tagged priority values assigned to the respective instruction threads. Priority values for individual threads may be updated with control software which tests thread performance and uses the test results to apply predetermined adjustment policies.

Abstract: Execution of a store instruction to modify an instruction at a memory location identified by a memory address is requested. A cache controller stores the memory address and the modified data in an associative memory coupled to a data cache and an instruction cache. In addition, the modified data is stored in a second level cache without invalidating the memory location associated with the instruction cache.

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: A cache within a computer system receives a partial write request and identifies a cache hit of a cache line. The cache line corresponds to the partial write request and includes existing data. In turn, the cache receives partial write data and merges the partial write data with the existing data into the cache line. In one embodiment, the existing data is “modified” or “dirty.” In another embodiment, the existing data is “shared.” In this embodiment, the cache changes the state of the cache line to indicate the storing of the partial write data into the cache line.

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: A method for minimizing cache conflict misses is disclosed. A translation table capable of facilitating the translation of a virtual address to a real address during a cache access is provided. The translation table includes multiple entries, and each entry of the translation table includes a page number field and a hash value field. A hash value is generated from a first group of bits within a virtual address, and the hash value is stored in the hash value field of an entry within the translation table. In response to a match on the entry within the translation table during a cache access, the hash value of the matched entry is retrieved from the translation table, and the hash value is concatenated with a second group of bits within the virtual address to form a set of indexing bits to index into a cache set.

Abstract: A processor resource manager assigns a branch history resource to a first execution mode. The branch history resource is utilized for predicting a branch direction of a branch instruction. Next, the resource manager logs a number of branch mispredictions that occur while the processor executes a second execution mode. The resource manager, in turn, reassigns the branch history resource to the second execution mode based upon the number of branch mispredictions.

Abstract: A processor blade determines whether a selected processing task is to be off-loaded to a storage blade for processing. The selected processing task is off-loaded to the storage blade via a planar bus communication path, in response to determining that the selected processing task is to be off-loaded to the storage blade. The off-loaded selected processing task is processed in the storage blade. The storage blade communicates the results of the processing of the off-loaded selected processing task to the processor blade.

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: A method, system and computer-usable medium are disclosed for managing prefetch streams in a virtual machine environment. Compiled application code in a first core, which comprises a Special Purpose Register (SPR) and a plurality of first prefetch engines, initiates a prefetch stream request. If the prefetch stream request cannot be initiated due to unavailability of a first prefetch engine, then an indicator bit indicating a Prefetch Stream Dispatch Fault is set in the SPR, causing a Hypervisor to interrupt the execution of the prefetch stream request. The Hypervisor then calls its associated operating system (OS), which determines prefetch engine availability for a second core comprising a plurality of second prefetch engines. If a second prefetch engine is available, then the OS migrates the prefetch stream request from the first core to the second core, where it is initiated on an available second prefetch engine.

Abstract: A method, system and computer-usable medium are disclosed for managing prefetch streams in a virtual machine environment. Compiled application code in a first core, which comprises a Special Purpose Register (SPR) and a plurality of first prefetch engines, initiates a prefetch stream request. If the prefetch stream request cannot be initiated due to unavailability of a first prefetch engine, then an indicator bit indicating a Prefetch Stream Dispatch Fault is set in the SPR, causing a Hypervisor to interrupt the execution of the prefetch stream request. The Hypervisor then calls its associated operating system (OS), which determines prefetch engine availability for a second core comprising a plurality of second prefetch engines. If a second prefetch engine is available, then the OS migrates the prefetch stream request from the first core to the second core, where it is initiated on an available second prefetch engine.

Abstract: A job scheduler can select a processor core operating frequency for a node in a cluster to perform a job based on energy usage and performance data. After a job request is received, an energy aware job scheduler accesses data that specifies energy usage and job performance metrics that correspond to the requested job and a plurality of processor core operating frequencies. A first of the plurality of processor core operating frequencies is selected that satisfies an energy usage criterion for performing the job based, at least in part, on the data that specifies energy usage and job performance metrics that correspond to the job. The job is assigned to be performed by a node in the cluster at the selected first of the plurality of processor core operating frequencies.