Abstract: The technology disclosed herein involves tracking contention and using the tracked contention to manage processor cache. The technology can be implemented in a processor's cache controlling logic and can enable the processor to track which locations in main memory are contentious. The technology can use the contentiousness of locations to determine where to store the data in cache and how to allocate and evict cache lines in the cache. In one example, the technology can store the data in a shared cache when the location is contentious and can bypass the shared cache and store the data in the private cache when the location is uncontentious. This may be advantageous because storing the data in shared cache can reduce or avoid having multiple copies in different private caches and can reduce the cache coherency overhead involved to keep copies in the private caches in sync.

Abstract: The technology disclosed herein involves tracking contention and using the tracked contention to reduce latency of exclusive memory operations. The technology enables a processor to track which locations in main memory are contentious and to modify the order exclusive memory operations are processed based on the contentiousness. A thread can include multiple exclusive operations for the same memory location (e.g., exclusive load and a complementary exclusive store). The multiple exclusive memory operations can be added to a queue and include one or more intervening operations between them in the queue. The processor may process the operations in the queue based on the order they were added and may use the tracked contention to perform out-of-order processing for some of the exclusive operations. For example, the processor can execute the exclusive load operation and because the corresponding location is contentious can process the complementary exclusive store operation before the intervening operations.

Abstract: The technology disclosed herein involves tracking contention and using the tracked contention to manage processor cache. The technology can be implemented in a processor’s cache controlling logic and can enable the processor to track which locations in main memory are contentious. The technology can use the contentiousness of locations to determine where to store the data in cache and how to allocate and evict cache lines in the cache. In one example, the technology can store the data in a shared cache when the location is contentious and can bypass the shared cache and store the data in the private cache when the location is uncontentious. This may be advantageous because storing the data in shared cache can reduce or avoid having multiple copies in different private caches and can reduce the cache coherency overhead involved to keep copies in the private caches in sync.

Abstract: The technology disclosed herein involves tracking contention and using the tracked contention to reduce latency of exclusive memory operations. The technology enables a processor to track which locations in main memory are contentious and to modify the order exclusive memory operations are processed based on the contentiousness. A thread can include multiple exclusive operations for the same memory location (e.g., exclusive load and a complementary exclusive store). The multiple exclusive memory operations can be added to a queue and include one or more intervening operations between them in the queue. The processor may process the operations in the queue based on the order they were added and may use the tracked contention to perform out-of-order processing for some of the exclusive operations. For example, the processor can execute the exclusive load operation and because the corresponding location is contentious can process the complementary exclusive store operation before the intervening operations.

Abstract: Systems and methods for coherency maintenance are presented. The systems and methods include utilization of multiple information state tracking approaches or protocols at different memory or storage levels. In one embodiment, a first coherency maintenance approach (e.g., similar to a MESI protocol, etc.) can be implemented at one storage level while a second coherency maintenance approach (e.g., similar to a MOESI protocol, etc.) can be implemented at another storage level. Information at a particular storage level or tier can be tracked by a set of local state indications and a set of essence state indications. The essence state indication can be tracked “externally” from a storage layer or tier directory (e.g., in a directory of another cache level, in a hub between cache levels, etc.). One storage level can control operations based upon the local state indications and another storage level can control operations based in least in part upon an essence state indication.

Abstract: Attributes of access requests can be used to distinguish one set of access requests from another set of access requests. The prefetcher can determine a pattern for each set of access requests and then prefetch cache lines accordingly. In an embodiment in which there are multiple caches, a prefetcher can determine a destination for prefetched cache lines associated with a respective set of access requests. For example, the prefetcher can prefetch one set of cache lines into one cache, and another set of cache lines into another cache. Also, the prefetcher can determine a prefetch distance for each set of access requests. For example, the prefetch distances for the sets of access requests can be different.

Abstract: Prefetching is permitted to cross from one physical memory page to another. More specifically, if a stream of access requests contains virtual addresses that map to more than one physical memory page, then prefetching can continue from a first physical memory page to a second physical memory page. The prefetching advantageously continues to the second physical memory page based on the confidence level and prefetch distance established while the first physical memory page was the target of the access requests.

Abstract: A system and method for managing cache replacements and a memory subsystem incorporating the system or the method. In one embodiment, the system includes: (1) a cache controller operable to control a cache and, in order: (1a) issue a pre-fetch command when the cache has a cache miss, (1b) perform at least one housekeeping task to ensure that the cache can store a replacement line and (1c) issue a fetch command and (2) a memory controller associated with a memory of a lower level than the cache and operable to respond to the pre-fetch command by performing at least one housekeeping task to ensure that the memory can provide the replacement line and respond to the fetch command by providing the replacement line.

Abstract: A system and method for managing cache replacements and a memory subsystem incorporating the system or the method. In one embodiment, the system includes: (1) a cache controller operable to control a cache and, in order: (1a) issue a pre-fetch command when the cache has a cache miss, (1b) perform at least one housekeeping task to ensure that the cache can store a replacement line and (1c) issue a fetch command and (2) a memory controller associated with a memory of a lower level than the cache and operable to respond to the pre-fetch command by performing at least one housekeeping task to ensure that the memory can provide the replacement line and respond to the fetch command by providing the replacement line.

Abstract: Cache hit information is used to manage (e.g., cap) the prefetch distance for a cache. In an embodiment in which there is a first cache and a second cache, where the second cache (e.g., a level two cache) has greater latency than the first cache (e.g., a level one cache), a prefetcher prefetches cache lines to the second cache and is configured to receive feedback from that cache. The feedback indicates whether an access request issued in response to a cache miss in the first cache results in a cache hit in the second cache. The prefetch distance for the second cache is determined according to the feedback.

Abstract: Systems and methods for coherency maintenance are presented. The systems and methods include utilization of multiple information state tracking approaches or protocols at different memory or storage levels. In one embodiment, a first coherency maintenance approach (e.g., similar to a MESI protocol, etc.) can be implemented at one storage level while a second coherency maintenance approach (e.g., similar to a MOESI protocol, etc.) can be implemented at another storage level. Information at a particular storage level or tier can be tracked by a set of local state indications and a set of essence state indications. The essence state indication can be tracked “externally” from a storage layer or tier directory (e.g., in a directory of another cache level, in a hub between cache levels, etc.). One storage level can control operations based upon the local state indications and another storage level can control operations based in least in part upon an essence state indication.

Abstract: Attributes of access requests can be used to distinguish one set of access requests from another set of access requests. The prefetcher can determine a pattern for each set of access requests and then prefetch cache lines accordingly. In an embodiment in which there are multiple caches, a prefetcher can determine a destination for prefetched cache lines associated with a respective set of access requests. For example, the prefetcher can prefetch one set of cache lines into one cache, and another set of cache lines into another cache. Also, the prefetcher can determine a prefetch distance for each set of access requests. For example, the prefetch distances for the sets of access requests can be different.

Abstract: Prefetching is permitted to cross from one physical memory page to another. More specifically, if a stream of access requests contains virtual addresses that map to more than one physical memory page, then prefetching can continue from a first physical memory page to a second physical memory page. The prefetching advantageously continues to the second physical memory page based on the confidence level and prefetch distance established while the first physical memory page was the target of the access requests.

Abstract: Cache hit information is used to manage (e.g., cap) the prefetch distance for a cache. In an embodiment in which there is a first cache and a second cache, where the second cache (e.g., a level two cache) has greater latency than the first cache (e.g., a level one cache), a prefetcher prefetches cache lines to the second cache and is configured to receive feedback from that cache. The feedback indicates whether an access request issued in response to a cache miss in the first cache results in a cache hit in the second cache. The prefetch distance for the second cache is determined according to the feedback.