Abstract: One embodiment of the present invention includes a microcontroller coupled to a memory management unit (MMU). The MMU is coupled to a page table included in a physical memory, and the microcontroller is configured to perform one or more virtual memory operations associated with the physical memory and the page table. In operation, the microcontroller receives a page fault generated by the MMU in response to an invalid memory access via a virtual memory address. To remedy such a page fault, the microcontroller performs actions to map the virtual memory address to an appropriate location in the physical memory. By contrast, in prior-art systems, a fault handler would typically remedy the page fault. Advantageously, because the microcontroller executes these tasks locally with respect to the MMU and the physical memory, latency associated with remedying page faults may be decreased. Consequently, overall system performance may be increased.

Abstract: A texture processing pipeline can be configured to service memory access requests that represent texture data access operations or generic data access operations. When the texture processing pipeline receives a memory access request that represents a texture data access operation, the texture processing pipeline may retrieve texture data based on texture coordinates. When the memory access request represents a generic data access operation, the texture pipeline extracts a virtual address from the memory access request and then retrieves data based on the virtual address. The texture processing pipeline is also configured to cache generic data retrieved on behalf of a group of threads and to then invalidate that generic data when the group of threads exits.

Abstract: A texture processing pipeline can be configured to service memory access requests that represent texture data access operations or generic data access operations. When the texture processing pipeline receives a memory access request that represents a texture data access operation, the texture processing pipeline may retrieve texture data based on texture coordinates. When the memory access request represents a generic data access operation, the texture pipeline extracts a virtual address from the memory access request and then retrieves data based on the virtual address. The texture processing pipeline is also configured to cache generic data retrieved on behalf of a group of threads and to then invalidate that generic data when the group of threads exits.

Abstract: Techniques are provided by which memory pages may be migrated among PPU memories in a multi-PPU system. According to the techniques, a UVM driver determines that a particular memory page should change ownership state and/or be migrated between one PPU memory and another PPU memory. In response to this determination, the UVM driver initiates a peer transition sequence to cause the ownership state and/or location of the memory page to change. Various peer transition sequences involve modifying mappings for one or more PPU, and copying a memory page from one PPU memory to another PPU memory. Several steps in peer transition sequences may be performed in parallel for increased processing speed.

Abstract: One embodiment of the present invention includes a microcontroller coupled to a memory management unit (MMU). The MMU is coupled to a page table included in a physical memory, and the microcontroller is configured to perform one or more virtual memory operations associated with the physical memory and the page table. In operation, the microcontroller receives a page fault generated by the MMU in response to an invalid memory access via a virtual memory address. To remedy such a page fault, the microcontroller performs actions to map the virtual memory address to an appropriate location in the physical memory. By contrast, in prior-art systems, a fault handler would typically remedy the page fault. Advantageously, because the microcontroller executes these tasks locally with respect to the MMU and the physical memory, latency associated with remedying page faults may be decreased. Consequently, overall system performance may be increased.

Abstract: One embodiment of the present invention is a parallel processing unit (PPU) that includes one or more streaming multiprocessors (SMs) and implements a replay unit per SM. Upon detecting a page fault associated with a memory transaction issued by a particular SM, the corresponding replay unit causes the SM, but not any unaffected SMs, to cease issuing new memory transactions. The replay unit then stores the faulting memory transaction and any faulting in-flight memory transaction in a replay buffer. As page faults are resolved, the replay unit replays the memory transactions in the replay buffer—removing successful memory transactions from the replay buffer—until all of the stored memory transactions have successfully executed. Advantageously, the overall performance of the PPU is improved compared to conventional PPUs that, upon detecting a page fault, stop performing memory transactions across all SMs included in the PPU until the fault is resolved.

Abstract: One embodiment of the present invention sets forth a technique for a program to access multi-dimensional formatted graphics surface memory. Multi-dimensional memory objects called “surfaces” stored in a user-specified data or pixel format and arranged in a graphics optimized layout are accessed by programs using surface instructions. A set of memory access instructions e.g., load, store, reduce, and atomic, referred to as surface instructions, may be used to access the surfaces. Coordinate bounds checking is performed with configurable clamping. Caching behavior may also be specified by the surface instructions. Data format conversion and packing to a specified storage format is supported for store, reduction, and atomic surface instructions. Data format conversion and unpacking from a specified storage format is supported for loads and atomic surface instructions.

Abstract: One embodiment of the present invention sets forth a computer-implemented method for migrating a memory page from a first memory to a second memory. The method includes determining a first page size supported by the first memory. The method also includes determining a second page size supported by the second memory. The method further includes determining a use history of the memory page based on an entry in a page state directory associated with the memory page. The method also includes migrating the memory page between the first memory and the second memory based on the first page size, the second page size, and the use history.

Abstract: One embodiment of the present invention sets forth a technique for performing aggregation operations across multiple threads that execute independently. Aggregation is specified as part of a barrier synchronization or barrier arrival instruction, where in addition to performing the barrier synchronization or arrival, the instruction aggregates (using reduction or scan operations) values supplied by each thread. When a thread executes the barrier aggregation instruction the thread contributes to a scan or reduction result, and waits to execute any more instructions until after all of the threads have executed the barrier aggregation instruction. A reduction result is communicated to each thread after all of the threads have executed the barrier aggregation instruction and a scan result is communicated to each thread as the barrier aggregation instruction is executed by the thread.

Abstract: A parallel counter accesses data generated by an application and stored within a register. The register includes different segments that include different portions of the application data. The parallel counter is configured to count the number of values within each segment that have a particular characteristic in a parallel fashion. The parallel counter may then return the individual segment counts to the application, or combine those segment counts and return a register count to the application. Advantageously, applications that rely on population count operations may be accelerated. Further, increasing the number of segments in a given register may reduce the time needed to count the values in that register, thereby providing a scalable solution to population counting. Additionally, the architecture of the parallel counter is sufficiently flexible to allow both register counting and segment counting, thereby combining two separate functionalities into just one hardware unit.

Abstract: One embodiment of the present invention is a memory subsystem that includes a sliding window tracker that tracks memory accesses associated with a sliding window of memory page groups. When the sliding window tracker detects an access operation associated with a memory page group within the sliding window, the sliding window tracker sets a reference bit that is associated with the memory page group and is included in a reference vector that represents accesses to the memory page groups within the sliding window. Based on the values of the reference bits, the sliding window tracker causes the selection a memory page in a memory page group that has fallen into disuse from a first memory to a second memory. Because the sliding window tracker tunes the memory pages that are resident in the first memory to reflect memory access patterns, the overall performance of the memory subsystem is improved.

Abstract: A tag unit configured to manage a cache unit includes a coalescer that implements a set hashing function. The set hashing function maps a virtual address to a particular content-addressable memory unit (CAM). The coalescer implements the set hashing function by splitting the virtual address into upper, middle, and lower portions. The upper portion is further divided into even-indexed bits and odd-indexed bits. The even-indexed bits are reduced to a single bit using a XOR tree, and the odd-indexed are reduced in like fashion. Those single bits are combined with the middle portion of the virtual address to provide a CAM number that identifies a particular CAM. The identified CAM is queried to determine the presence of a tag portion of the virtual address, indicating a cache hit or cache miss.

Abstract: One embodiment of the present invention sets forth a technique for performing a method for synchronizing divergent executing threads. The method includes receiving a plurality of instructions that includes at least one set-synchronization instruction and at least one instruction that includes a synchronization command, and determining an active mask that indicates which threads in a plurality of threads are active and which threads in the plurality of threads are disabled. For each instruction included in the plurality of instructions, the instruction is transmitted to each of the active threads included in the plurality of threads. If the instruction is a set-synchronization instruction, then a synchronization token, the active mask and the synchronization point is each pushed onto a stack.

Abstract: A texture processing pipeline can be configured to service memory access requests that represent texture data access operations or generic data access operations. When the texture processing pipeline receives a memory access request that represents a texture data access operation, the texture processing pipeline may retrieve texture data based on texture coordinates. When the memory access request represents a generic data access operation, the texture pipeline extracts a virtual address from the memory access request and then retrieves data based on the virtual address. The texture processing pipeline is also configured to cache generic data retrieved on behalf of a group of threads and to then invalidate that generic data when the group of threads exits.

Abstract: A tag unit configured to manage a cache unit includes a coalescer that implements a set hashing function. The set hashing function maps a virtual address to a particular content-addressable memory unit (CAM). The coalescer implements the set hashing function by splitting the virtual address into upper, middle, and lower portions. The upper portion is further divided into even-indexed bits and odd-indexed bits. The even-indexed bits are reduced to a single bit using a XOR tree, and the odd-indexed are reduced in like fashion. Those single bits are combined with the middle portion of the virtual address to provide a CAM number that identifies a particular CAM. The identified CAM is queried to determine the presence of a tag portion of the virtual address, indicating a cache hit or cache miss.

Abstract: One embodiment of the present invention sets forth a technique providing an optimized way to allocate and access memory across a plurality of thread/data lanes. Specifically, the device driver receives an instruction targeted to a memory set up as an array of structures of arrays. The device driver computes an address within the memory using information about the number of thread/data lanes and parameters from the instruction itself. The result is a memory allocation and access approach where the device driver properly computes the target address in the memory. Advantageously, processing efficiency is improved where memory in a parallel processing subsystem is internally stored and accessed as an array of structures of arrays, proportional to the SIMT/SIMD group width (the number of threads or lanes per execution group).

Abstract: One embodiment of the present invention sets forth a technique for performing aggregation operations across multiple threads that execute independently. Aggregation is specified as part of a barrier synchronization or barrier arrival instruction, where in addition to performing the barrier synchronization or arrival, the instruction aggregates (using reduction or scan operations) values supplied by each thread. When a thread executes the barrier aggregation instruction the thread contributes to a scan or reduction result, and waits to execute any more instructions until after all of the threads have executed the barrier aggregation instruction. A reduction result is communicated to each thread after all of the threads have executed the barrier aggregation instruction and a scan result is communicated to each thread as the barrier aggregation instruction is executed by the thread.

Abstract: One embodiment of the present invention sets forth a technique for efficiently performing voting operations within a multi-threaded parallel-processing system. A group of related parallel program threads executes within a processor core together in parallel. A new instruction, called a “vote” instruction, is introduced that enables a parallel program thread to post an individual vote within the context of the group of related threads and to receive the result of the vote. In this fashion, the vote instruction advantageously reduces overhead associated with inter-thread communication, thereby improving overall system performance.

Abstract: One embodiment of the present invention sets forth a technique for efficiently performing voting operations within a multi-threaded parallel-processing system. A group of related parallel program threads executes within a processor core together in parallel. A new instruction, called a “vote” instruction, is introduced that enables a parallel program thread to post an individual vote within the context of the group of related threads and to receive the result of the vote. In this fashion, the vote instruction advantageously reduces overhead associated with inter-thread communication, thereby improving overall system performance.

Abstract: One embodiment of the present invention sets forth a technique for efficiently performing voting operations within a multi-threaded parallel-processing system. A group of related parallel program threads executes within a processor core together in parallel. A new instruction, called a “vote” instruction, is introduced that enables a parallel program thread to post an individual vote within the context of the group of related threads and to receive the result of the vote. In this fashion, the vote instruction advantageously reduces overhead associated with inter-thread communication, thereby improving overall system performance.