Samsung Electronics Co., Ltd.

David Black-Schaffer

Erik Hagersten

Andreas Sembrant

Stefanos Kaxiras

Stafanos Kaxiras

Erik Ernst Hagersten

Andreas Karl Sembrant

Data units are stored in private caches in nodes of a multiprocessor system, each node containing at least one processor (CPU), at least one cache private to the node and at least one cache location buffer (CLB) private to the node. In each CLB location information values are stored, each location information value indicating a location associated with a respective data unit, wherein each location information value stored in a given CLB indicates the location to be either a location within the private cache disposed in the same node as the given CLB, to be a location in one of the other nodes, or to be a location in a main memory. Coherence of values of the data units is maintained using a cache coherence protocol. The location information values stored in the CLBs are updated by the cache coherence protocol in accordance with movements of their respective data units.

Systems and methods for implementing coherent memory in a multiprocessor system

Data units are stored in private caches in nodes of a multiprocessor system, each node containing at least one processor (CPU), at least one cache private to the node and at least one cache locations buffer {CLB} private to the node. In each CLB location information values are stored, each location information value indicating a location associated with a respective data unit, wherein each location information value stored in a given CLB indicates the location to be either a location within the private cache disposed in the same node as the given CLB, to be a location in one of the other nodes, or to be a location in a main memory. Coherence of values of the data units is maintained using a cache coherence protocol The location information values stored in the CLBs are updated by the cache coherence protocol in accordance with movements of their respective data units.

A data management method for a processor to which a first cache, a second cache, and a behavior history table are allocated, includes tracking reuse information learning cache lines stored in at least one of the first cache and the second cache; recording the reuse information in the behavior history table; and determining a placement policy with respect to future operations that are to be performed on a plurality of cache lines stored in the first cache and the second cache, based on the reuse information in the behavior history table.

Systems and methods for efficient cacheline handling based on predictions

Caches may be vulnerable to side-channel attacks, such as Spectre and Meltdown, that involve speculative execution of instructions, revealing information about a cache that the attacker is not permitted to access. Access permission may be stored in the cache, such as in an entry of a cache table or in the region information for a cache table. Optionally, the access permission may be re-checked if the access permission changes while a memory instruction is pending. Optionally, a random index value may be stored in a cache and used, at least in part, to identify a memory location of a cacheline. Optionally, cachelines that are involved in speculative loads for memory instructions may be marked as speculative. On condition of resolving the speculative load as non-speculative, the cacheline may be marked as non-speculative; and on condition of resolving the speculative load as mis-speculated, the cacheline may be removed from the cache.

System protecting caches from side-channel attacks

A multiprocessor system includes a plurality of nodes and at least one memory, wherein each node includes at least one processor, a first cache private to the node, a second cache at a higher level than the first cache, and a cache location buffer (CLB) private to the node, wherein, for at least one node of the plurality of nodes, at least one of the first cache and the second cache included in the at least one node includes at least one cache location that is capable of storing a compressed data unit of varying size, the CLB included in the at least one node is configured to store a plurality of CLB entries, each of the CLB entries including a plurality of location information values.

Systems and methods for efficient compressed cache line storage and handling

Data units are stored in private caches in nodes of a multiprocessor system, each node containing at feast one processor (CPU), at least one cache private to the node and at least one cache location buffer {CLB} private to the node. In each CLB location information values are stored, each location information value indicating a location associated with a respective data unit, wherein each location information value stored in a given CLB indicates the location to be either a location within the private cache disposed in the same node as the given CLB, to be a location in one of the other nodes, or to be a location in a main memory. Coherence of values of the data units is maintained using a cache coherence protocol The location information values stored in the CLBs are updated by the cache coherence protocol in accordance with movements of their respective data units.

Methods and systems which, for example, reduce energy usage in cache memories are described. Cache location information regarding the location of cachelines which are stored in a tracked portion of a memory hierarchy is stored in a cache location table. Address tags are stored with corresponding location information in the cache location table to associate the address tag with the cacheline and its cache location information. When a cacheline is moved to a new location in the memory hierarchy, the cache location table is updated so that the cache location information indicates where the cacheline is located within the memory hierarchy.

Systems and methods for reducing first level cache energy by eliminating cache address tags

The execution or processing of an application can be adapted or modified based on a level of a cache in which a requested data block resides, by extracting level information from a cache hierarchy. When a request for a data block is made by a core to a cache memory system, the cache memory system extracts a level of a cache memory in which the data block resides from information stored in the cache memory system. The core is informed of the level of the cache memory in which the data block resides, and uses this information to adapt its processing of the application.

Management of shared pipeline resource usage based on level information

Methods and systems for in direct data access in, e.g., multi-level cache memory systems are described. A cache memory system includes a cache location buffer configured to store cache location entries, wherein each cache location entry includes an address tag and a cache location table which are associated with a respective cacheline stored in a cache memory. The system also includes a first cache memory configured to store cachelines, each cacheline having data and an identity of a corresponding cache location entry in the cache location buffer, and a second cache memory configured to store cachelines, each cacheline having data and an identity of a corresponding cache location entry in the cache location buffer. Responsive to a memory access request for a cacheline, the cache location buffer generates access information using one of the cache location tables which enables access to the cacheline without performing a tag comparison at the one of the first and second cache memories.

Systems and methods for direct data access in multi-level cache memory hierarchies

A computer processing system includes a plurality of nodes, each node having at least one processor core and at least one level of cache memory which is private to the node, a shared, last level cache (LLC) memory device and a shared, last level cache location buffer containing cache location entries, each cache location entry storing an address tag and a plurality of location information. The location information stored in a cache location entry points to an identified cacheline location within the LLC that stores a cacheline associated with the location information. The cacheline stored in the LLC has associated information identifying the cache location entry.

Systems and methods for implementing a tag-less shared cache and a larger backing cache

Data can be stored in a multi-level cache hierarchy memory system by, for example, storing valid data associated with a cacheline in a primary location in a first cache memory location. The first cache memory also stores location information about an alternative location in a second cache memory associated with the cacheline. Space is allocated in the alternative location of the second cache memory to store data associated with the cacheline.

Tracking alternative cacheline placement locations in a cache hierarchy

A placement policy enables the selective storage of cachelines in a multi-level cache hierarchy: Reuse behavior of a cacheline is tracked during execution of an application in both a first level cache memory and a second level cache memory. A cache placement policy for the cacheline is determined based on the tracked reuse behavior.

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Uppsala, Sweden

David Black-Schaffer