US 5,490,260 A · Solid-state RAM data storage for virtual memory computer using fixed-sized swap pages with selective compressed/uncompressed data store according to each data size

Abstract

A computer using virtual memory management employs a random-access type storage device such as a semiconductor memory for page swapping. The semiconductor memory is formatted to provide multiple partitions of varying block size, e.g., two block sizes, for compressed pages, and another block size for uncompressed original-sized pages. The data to be stored is in pages of fixed size, and these pages are compressed for storage if the compressed size fits in the block size of one of the small-block partitions in the memory. If a data page is not compressible to one of the small block sizes, it is stored uncompressed in the other full-size partition. The operating system maintains a table storing the locations of the pages in the partitions, so upon recall the page (if compressed) is retrieved from its location found using the table, decompressed and sent to the CPU. The relative number of blocks in the partitioned memory (e.g., the physical storage capacity of the memory) is set (or dynamically allocated) at the average ratio of compressible pages to uncompressible pages for the compression algorithm used. For example, an algorithm may compress 90% of the pages to either 50% or 70% of their original size, so a ratio of the number of locations in the compressed partitions of the semiconductor memory to the number of locations in the uncompressed partition is selected as 90:10. The compression mechanism operates on bytes in bit-parallel format, and uses a lookahead buffer which is compared with bytes in a window to produce 9-bit symbols. The stream of 9-bit symbols passes through an ECC generator, also operating in bit-parallel.

Claims20

Dependent claims

A method of storing pages of data in a semiconductor memory, the pages of data being of fixed size before compression, said method comprising the steps of:

a) partitioning the semiconductor memory to provide first, second, and third memory spaces, each of said memory spaces containing a large number of memory locations, the memory locations of the first memory space being of a first size for storing one of said pages of data compressed to at most said first size, the memory locations of the second memory space being of a second size for storing one of said pages of data compressed to at most said second size;
the memory locations of said third memory space being of said fixed size;
b) receiving said pages of data from a data source and compressing each of said pages of data to produce a compressed page, and detecting if each said compressed page is as small as said first size and is as small as said second size, and producing an output indicative of the size of each compressed page;
c) storing each of said compressed pages of data in said semiconductor memory, a compressed page being stored in said first memory space in response to said output from said step of detecting if a compressed page is of said first size, and a compressed page being stored in said second memory space in response to said output of said step of detecting if a compressed page is of said second size, and, if a page is not compressed to as small as either said first or second size, then said page uncompressed in said third memory space.

1 more element

A method of storing page-swap data in a virtual memory system, comprising the steps of:

storing in a semiconductor memory unit a large number of swap pages which are (a) compressed to a first level no more than a first value and stored in a first area of said memory if compressible to said first level, and Co) compressed to a second level no more than a second value but greater than said first value and stored in a second area of said memory if compressible to said second level, and (c) if not compressible to said second level then stored uncompressed in a third area of said memory;
recording the number of pages stored in each of said first, second and third areas as recorded numbers;
partitioning said memory in response to said recorded numbers to provide altered boundaries between said first, second and third areas defined by addresses, and again storing said page-swap data in a minimum of space in said memory;
said altered boundaries re-defining said first, second, and third memory areas, said first memory area having blocks of said first value, said second memory area having blocks of said second value, and said third memory area having blocks of a size equal to that of said swap pages when said swap pages are stored uncompressed.

1 more element

Dependencies are inferred from the claim text.

Solid-state RAM data storage for virtual memory computer using fixed-sized swap pages with selective compressed/uncompressed data store according to each data size

Life of this patent

Solid-state RAM data storage for virtual memory computer using fixed-sized swap pages with selective compressed/uncompressed data store according to each data size

Life of this patent

Abstract

Claims20