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 system for managing virtual memory. The system includes a first processing unit configured to execute a first operation that references a first virtual memory address. The system also includes a first memory management unit (MMU) associated with the first processing unit and configured to generate a first page fault upon determining that a first page table that is stored in a first memory unit associated with the first processing unit does not include a mapping corresponding to the first virtual memory address. The system further includes a first copy engine associated with the first processing unit. The first copy engine is configured to read a first command queue to determine a first mapping that corresponds to the first virtual memory address and is included in a first page state directory. The first copy engine is also configured to update the first page table to include the first mapping.

Abstract: A system for managing virtual memory. The system includes a first processing unit configured to execute a first operation that references a first virtual memory address. The system also includes a first memory management unit (MMU) associated with the first processing unit and configured to generate a first page fault upon determining that a first page table that is stored in a first memory unit associated with the first processing unit does not include a mapping corresponding to the first virtual memory address. The system further includes a first copy engine associated with the first processing unit. The first copy engine is configured to read a first command queue to determine a first mapping that corresponds to the first virtual memory address and is included in a first page state directory. The first copy engine is also configured to update the first page table to include the first mapping.

Abstract: One embodiment of the present invention includes a memory management unit (MMU) that is configured to manage sparse mappings. The MMU processes requests to translate virtual addresses to physical addresses based on page table entries (PTEs) that indicate a sparse status. If the MMU determines that the PTE does not include a mapping from a virtual address to a physical address, then the MMU responds to the request based on the sparse status. If the sparse status is active, then the MMU determines the physical address based on whether the type of the request is a write operation and, subsequently, generates an acknowledgement of the request. By contrast, if the sparse status is not active, then the MMU generates a page fault. Advantageously, the disclosed embodiments enable the computer system to manage sparse mappings without incurring the performance degradation associated with both page faults and conventional software-based sparse mapping management.

Abstract: A system for managing virtual memory. The system includes a first processing unit configured to execute a first operation that references a first virtual memory address. The system also includes a first memory management unit (MMU) associated with the first processing unit and configured to generate a first page fault upon determining that a first page table that is stored in a first memory unit associated with the first processing unit does not include a mapping corresponding to the first virtual memory address. The system further includes a first copy engine associated with the first processing unit. The first copy engine is configured to read a first command queue to determine a first mapping that corresponds to the first virtual memory address and is included in a first page state directory. The first copy engine is also configured to update the first page table to include the first mapping.

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 system for managing virtual memory. The system includes a first processing unit configured to execute a first operation that references a first virtual memory address. The system also includes a first memory management unit (MMU) associated with the first processing unit and configured to generate a first page fault upon determining that a first page table that is stored in a first memory unit associated with the first processing unit does not include a mapping corresponding to the first virtual memory address. The system further includes a first copy engine associated with the first processing unit. The first copy engine is configured to read a first command queue to determine a first mapping that corresponds to the first virtual memory address and is included in a first page state directory. The first copy engine is also configured to update the first page table to include the first mapping.

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 includes a memory management unit (MMU) that is configured to efficiently process requests to access memory that includes protected regions. Upon receiving an initial request via a virtual address (VA), the MMU translates the VA to a physical address (PA) based on page table entries (PTEs) and gates the response based on page-specific secure state information. To thwart software-based attempts to illicitly access the protected regions, the secure state information is not stored in page tables. However, to expedite subsequent requests, after the MMU identifies the PTE and the corresponding secure state information, the MMU stores both the PTE and the secure state information as a cache line in a translation lookaside buffer.

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 performing a method for compressing page table entries (PTEs) prior to storing the PTEs in a translation look-aside buffer (TLB). A page table entry (PTE) request is received for a PTE that is not stored in the TLB. The PTE as well as a plurality of PTEs that are adjacent to the PTE are retrieved from a memory. The PTE and the plurality of PTEs are compressed and then stored in the TLB.

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 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 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 system and method are provided for protecting data. In operation, a request to read data from memory is received. Additionally, it is determined whether the data is stored in a predetermined portion of the memory. If it is determined that the data is stored in the predetermined portion of the memory, the data and a protect signal are returned for use in protecting the data. In certain embodiments of the invention, data stored in the predetermined portion of the memory may be further processed and written hack to the predetermined portion of the memory. In other embodiments of the invention, such processing may involve unprotected data stored outside the predetermined portion of the memory.

Abstract: A system and method are provided for implementing multi-stage translation of virtual addresses. The method includes the steps of receiving, at a first memory management unit, a memory request including a virtual address in a first address space, translating the virtual address to generate a second virtual address in a second address space, and transmitting a modified memory request including the second virtual address to a second memory management unit. The second memory management unit is configured to translate the second virtual address to generate a physical address in a third address space. The physical address is associated with a location in a memory.

Abstract: One embodiment of the present invention includes a memory management unit (MMU) that is configured to manage sparse mappings. The MMU processes requests to translate virtual addresses to physical addresses based on page table entries (PTEs) that indicate a sparse status. If the MMU determines that the PTE does not include a mapping from a virtual address to a physical address, then the MMU responds to the request based on the sparse status. If the sparse status is active, then the MMU determines the physical address based on whether the type of the request is a write operation and, subsequently, generates an acknowledgement of the request. By contrast, if the sparse status is not active, then the MMU generates a page fault. Advantageously, the disclosed embodiments enable the computer system to manage sparse mappings without incurring the performance degradation associated with both page faults and conventional software-based sparse mapping management.

Abstract: One embodiment of the present invention includes techniques to support demand paging across a processing unit. Before a host unit transmits a command to an engine that does not tolerate page faults, the host unit ensures that the virtual memory addresses associated with the command are appropriately mapped to physical memory addresses. In particular, if the virtual memory addresses are not appropriately mapped, then the processing unit performs actions to map the virtual memory address to appropriate locations in physical memory. Further, the processing unit ensures that the access permissions required for successful execution of the command are established. Because the virtual memory address mappings associated with the command are valid when the engine receives the command, the engine does not encounter page faults upon executing the command. Consequently, in contrast to prior-art techniques, the engine supports demand paging regardless of whether the engine is involved in remedying page faults.

Abstract: A system for managing virtual memory. The system includes a first processing unit configured to execute a first operation that references a first virtual memory address. The system also includes a first memory management unit (MMU) associated with the first processing unit and configured to generate a first page fault upon determining that a first page table that is stored in a first memory unit associated with the first processing unit does not include a mapping corresponding to the first virtual memory address. The system further includes a first copy engine associated with the first processing unit. The first copy engine is configured to read a first command queue to determine a first mapping that corresponds to the first virtual memory address and is included in a first page state directory. The first copy engine is also configured to update the first page table to include the first mapping.