Qualcomm Incorporated

Richard Senior

Gurvinder Singh Chhabra

Nieyan Geng

Amin Ansari

Andres Alejandro Oportus Valenzuela

Vito Remo Bica

Anand Janakiraman

Raghuveer Raghavendra

Christopher E Koob

Jinxia Bai

Christopher Porter

Adrienne Milner

Sundeep Kushwaha

Kan Wang

Norris Geng

Richard Alan Stewart

Arvind Krishnaswamy

Maksim Krasnyanskiy

Can Acar

Christopher Ahn

Unni Prasad

Harsha Gordhan Jagasia

A compressed memory system of a processor-based system includes a memory partitioning circuit for partitioning a memory region into data regions with different priority levels. The system also includes a cache line selection circuit for selecting a first cache line from a high priority data region and a second cache line from a low priority data region. The system also includes a compression circuit for compressing the cache lines to obtain a first and a second compressed cache line. The system also includes a cache line packing circuit for packing the compressed cache lines such that the first compressed cache line is written to a first predetermined portion and the second cache line or a portion of the second compressed cache line is written to a second predetermined portion of the candidate compressed cache line. The first predetermined portion is larger than the second predetermined portion.

Priority-based cache-line fitting in compressed memory systems of processor-based systems

A compressed memory system includes a memory region that includes cache lines having priority levels. The compressed memory system also includes a compressed memory region that includes compressed cache lines. Each compressed cache line includes a first set of data bits configured to hold, in a first direction, either a portion of a first cache line or a portion of the first cache line after compression, the first cache line having a first priority level. Each compressed cache line also includes a second set of data bits configured to hold, in a second direction opposite to the first direction, either a portion of a second cache line or a portion of the second cache line after compression, the second cache line having a priority level lower than the first priority level. The first set of data bits includes a greater number of bits than the second set of data bits.

A method of managing a stack includes detecting, by a stack manager of a processor, that a size of a frame to be allocated exceeds available space of a first stack. The first stack is used by a particular task executing at the processor. The method also includes designating a second stack for use by the particular task. The method further includes copying metadata associated with the first stack to the second stack. The metadata enables the stack manager to transition from the second stack to the first stack upon detection that the second stack is no longer in use by the particular task. The method also includes allocating the frame in the second stack.

Stack management

Various embodiments include methods and devices for generating a memory map configured to map virtual addresses of pages to physical addresses, in which pages of a same size are grouped into regions. The embodiments may include adding a first entry for a first additional page to a first region in the memory map, shifting virtual addresses of the first region to accommodate a shift of virtual addresses of the first region allocated for code by a sub-page granular shift amount, mapping shifted virtual addresses of the first entry for the first additional page to physical address mapped to a first lowest shifted virtually addressed page of the first region, and shifting the virtual addresses of the first region allocated for code by a sub-page granular shift amount, in which the virtual addresses of the first region allocated for code partially shift into the first entry for the first additional page.

Increasing address space layout randomization entropy via page remapping and rotations

In an aspect, high priority lines are stored starting at an address aligned to a cache line size for instance 64 bytes, and low priority lines are stored in memory space left by the compression of high priority lines. The space left by the high priority lines and hence the low priority lines themselves are managed through pointers also stored in memory. In this manner, low priority lines contents can be moved to different memory locations as needed. The efficiency of higher priority compressed memory accesses is improved by removing the need for indirection otherwise required to find and access compressed memory lines, this is especially advantageous for immutable compressed contents. The use of pointers for low priority is advantageous due to the full flexibility of placement, especially for mutable compressed contents that may need movement within memory for instance as it changes in size over time.

Priority-based storage and access of compressed memory lines in memory in a processor-based system

Reducing bandwidth consumption when performing free memory list cache maintenance in compressed memory schemes of processor-based systems is disclosed. In this regard, a memory system including a compression circuit is provided. The compression circuit includes a compress circuit that is configured to cache free memory lists using free memory list caches comprising a plurality of buffers. When a number of pointers cached within the free memory list cache falls below a low threshold value, an empty buffer of the plurality of buffers is refilled from a system memory. In some aspects, when a number of pointers of the free memory list cache exceeds a high threshold value, a full buffer of the free memory list cache is emptied to the system memory. In this manner, memory access operations for emptying and refilling the free memory list cache may be minimized.

Reducing bandwidth consumption when performing free memory list cache maintenance in compressed memory schemes of processor-based systems

Reducing metadata size in compressed memory systems of processor-based systems is disclosed. In one aspect, a compressed memory system provides 2compressed data regions, corresponding 2sets of free memory lists, and a metadata circuit. The metadata circuit associates virtual addresses with abbreviated physical addresses, which omit N upper bits of corresponding full physical addresses, of memory blocks of the 2compressed data regions. A compression circuit of the compressed memory system receives a memory access request including a virtual address, and selects one of the 2compressed data regions and one of the 2sets of free memory lists based on a modulus of the virtual address and 2. The compression circuit retrieves an abbreviated physical address corresponding to the virtual address from the metadata circuit, and performs a memory access operation on a memory block associated with the abbreviated physical address in the selected compressed data region.

Reducing metadata size in compressed memory systems of processor-based systems

Aspects for generating compressed data streams with lookback pre-fetch instructions are disclosed. A data compression system is provided and configured to receive and compress an uncompressed data stream as part of a lookback-based compression scheme. The data compression system determines if a current data block was previously compressed. If so, the data compression system is configured to insert a lookback instruction corresponding to the current data block into the compressed data stream. Each lookback instruction includes a lookback buffer index that points to an entry in a lookback buffer where decompressed data corresponding to the data block will be stored during a separate decompression scheme. Once the data blocks have been compressed, the data compression system is configured to move a lookback buffer index of each lookback instruction in the compressed data stream into a lookback pre-fetch instruction located earlier than the corresponding lookback instruction in the compressed data stream.

Generating compressed data streams with lookback pre-fetch instructions for pre-fetching decompressed data from a lookback buffer

Aspects disclosed involve reducing or avoiding buffering of evicted cache data from an uncompressed cache memory in a compression memory system when stalled write operations occur. A processor-based system is provided that includes a cache memory and a compression memory system. When a cache entry is evicted from the cache memory, cache data and a virtual address associated with the evicted cache entry are provided to the compression memory system. The compression memory system reads metadata associated with the virtual address of the evicted cache entry to determine the physical address in the compression memory system mapped to the evicted cache entry. If the metadata is not available, the compression memory system stores the evicted cache data at a new, available physical address in the compression memory system without waiting for the metadata. Thus, buffering of the evicted cache data to avoid or reduce stalling write operations is not necessary.

Reducing or avoiding buffering of evicted cache data from an uncompressed cache memory in a compression memory system when stalled write operations occur

A system for data decompression may include a processor coupled to a remote memory having a remote dictionary stored thereon and coupled to a decompression logic having a local memory with a local dictionary. The processor may decompress data during execution by accessing the local dictionary, and if necessary, the remote dictionary.

System, apparatus, and method for decompressing data

Aspects disclosed relate to a priority-based access of compressed memory lines in a processor-based system. In an aspect, a memory access device in the processor-based system receives a read access request for memory. If the read access request is higher priority, the memory access device uses the logical memory address of the read access request as the physical memory address to access the compressed memory line. However, if the read access request is lower priority, the memory access device translates the logical memory address of the read access request into one or more physical memory addresses in memory space left by the compression of higher priority lines. In this manner, the efficiency of higher priority compressed memory accesses is improved by removing a level of indirection otherwise required to find and access compressed memory lines.

Priority-based access of compressed memory lines in memory in a processor-based system

Aspects include computing devices, systems, and methods for implementing executing decompression of a compressed page. A computing device may determine a decompression block belonging to a compressed page that contains a code instruction requested in a memory access request. Decompression blocks, other than the decompression block containing the requested code instruction, may be selected for decompression based on their locality with respect to the decompression block containing the requested code instruction. Decompression blocks not identified for decompression may be substituted for a fault or exception code. The computing device may decompress decompression blocks identified for decompression, terminating the decompression of the compressed page upon filling all blocks with decompressed blocks, faults, or exception code. The remaining decompression blocks belonging to the compressed page may be decompressed after or concurrently with the execution of the requested code instruction.

Efficient decompression locality system for demand paging

Aspects include computing devices, systems, and methods for implementing executing decompression of a compressed page. A computing device may determine a decompression block of a compressed page that contains a code instruction requested in a memory access request. Decompression blocks, other than the decompression block containing the requested code instruction, may be selected for decompression based on being situated between an end of the compressed page and the decompression block containing the requested code instruction. Decompression blocks not identified for decompression may be substituted for a fault or exception code. The computing device may decompress decompression blocks identified for decompression, starting at the end of the compressed page and terminating the decompression of the compressed page upon filling all blocks with decompressed blocks, faults, or exception code. The remaining decompression blocks of the compressed page may be decompressed after or concurrently with the execution of the requested code instruction.

Reducing decompression time without impacting compression ratio

Data compression systems, methods, and computer program products are disclosed. For each successive input word of an input stream, it is determined whether the input word matches an entry in a lookback table. The lookback table is updated in response to the input word. Input words may be of a number of data types, including zero runs and full or partial matches with an entry in the lookback table. A codeword is generated by entropy encoding a data type corresponding to the input word. The lookback table may be indexed by the position of the input word in the input stream.

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San Diego, CA, United States of America

Richard Senior