摘要:
A method and apparatus for preventing selection of Deleted (D) members as an LRU victim during LRU victim selection. During each cache access targeting the particular congruence class, the deleted cache line is identified from information in the cache directory. A location of a deleted cache line is pipelined through the cache architecture during LRU victim selection. The information is latched and then passed to MRU vector generation logic. An MRU vector is generated and passed to the MRU update logic, which is selects/tags the deleted member as a MRU member. The make MRU operation affects only the lower level LRU state bits arranged in a tree-based structure state bits so that the make MRU operation only negates selection of the specific member in the D state, without affecting LRU victim selection of the other members.
摘要:
A method of handling a stuck bit in a directory of a cache memory, by defining multiple binary encodings to indicate a defective cache state, detecting an error in a tag stored in a member of the directory (wherein the tag at least includes an address field, a state field and an error-correction field), determining that the error is associated with a stuck bit of the directory member, and writing new state information to the directory member which is selected from one of the binary encodings based on a field location of the stuck bit within the directory member. The multiple binary encodings may include a first binary encoding when the stuck bit is in the address field, a second binary encoding when the stuck bit is in the state field, and a third binary encoding when the stuck bit is in the error-correction field. The new state information may also further be selected based on the value of the stuck bit, e.g., a state bit corresponding to the stuck bit is assigned a bit value from the new state information which matches the value of the stuck bit.
摘要:
A method of handling a stuck bit in a directory of a cache memory which detects an error in a stored tag having an address field, a state field and an error-correction field, determines that the error is associated with a stuck bit of the directory member, marks the directory member as defective, and casts out corrected address information. The error is detected during processing of a cache directory access request, and is determined to be associated with a stuck bit of the directory member by attempting to correct a first error and then detecting a second error after the first correction attempt. The address information is cast out by routing a surrogate tag contained in a surrogate member of the cache directory through error-correction pipeline circuitry while transmitting the address information from the surrogate member to a cast-out machine.
摘要:
A method of handling a stuck bit in a directory of a cache memory, by defining multiple binary encodings to indicate a defective cache state, detecting an error in a tag stored in a member of the directory (wherein the tag at least includes an address field, a state field and an error-correction field), determining that the error is associated with a stuck bit of the directory member, and writing new state information to the directory member which is selected from one of the binary encodings based on a field location of the stuck bit within the directory member. The multiple binary encodings may include a first binary encoding when the stuck bit is in the address field, a second binary encoding when the stuck bit is in the state field, and a third binary encoding when the stuck bit is in the error-correction field. The new state information may also further be selected based on the value of the stuck bit, e.g., a state bit corresponding to the stuck bit is assigned a bit value from the new state information which matches the value of the stuck bit.
摘要:
A method utilizes information provided by performance monitoring hardware to dynamically adjust the number of levels of speculative branch predictions allowed (typically 3 or 4 per thread) for a processor core. The information includes cycles-per-instruction (CPI) for the processor core and number of memory accesses per unit time. If the CPI is below a CPI threshold; and the number of memory accesses (NMA) per unit time is above a prescribed threshold, the number of levels of speculative branch predictions is reduced per thread for the processor core. Likewise, the number of levels of speculative branch predictions could be increased, from a low level to maximum allowed, if the CPI threshold is exceeded or the number of memory accesses per unit time is below the prescribed threshold.
摘要:
A method, system and computer-usable medium are disclosed for managing transient instruction streams. Transient flags are defined in Branch-and-Link (BRL) instructions that are known to be infrequently executed. A bit is likewise set in a Special Purpose Register (SPR) of the hardware (e.g., a core) that is executing an instruction request thread. Subsequent fetches or prefetches in the request thread are treated as transient and are not written to lower-level caches. If an instruction is non-transient, and if a lower-level cache is non-inclusive of the L1 instruction cache, a fetch or prefetch miss that is obtained from memory may be written in both the L1 and the lower-level cache. If it is not inclusive, a cast-out from the L1 instruction cache may be written in the lower-level cache.
摘要:
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.
摘要:
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.
摘要:
A performance projection system includes a test IHS and multiple currently existing IHSs. The performance projection system includes user application software and surrogate programs that execute on currently existing IHSs. The performance projection system measures user application software and surrogate program performance during execution on currently existing IHSs. The performance projection systems measures runtime program performance during execution of surrogate programs on a future semiconductor die IC design model or virtualized future system. Designers normalize and compare surrogate program runtime performance data with user application software performance data. Designers un-normalize the normalized runtime performance data to generate a projection of runtime performance on the future system.
摘要:
A multiprocessor system which includes automatic workload distribution. As threads execute in the multiprocessor system, an operating system or hypervisor continuously learns the execution characteristics of the threads and saves the information in thread-specific control blocks. The execution characteristics are used to generate thread performance data. As the thread executes, the operating system continuously uses the performance data to steer the thread to a core that will execute the workload most efficiently.