MemoryExpansion Technology (MXT): Software support and performance A novel memory subsystem called Memory Expansion Technology (MXT) has been built for fast hardware compression of main-memory content. This allows a memory expansion to present a "real" memory larger than the physically available memory. This paper provides an overview of the memorycompression architecture, its OS support under Linux and Windows ® , and an analysis of the performance impact of memory compression. Results show that the hardware compression of main memory has a negligible penalty compared to an uncompressed main memory, and for memory-starved applications it increases performance significantly. We also show that the memory content of an application can usually be compressed by a factor of 2.
Several technologies are leveraged to establish an architecture for a low-cost, highperformance memory controller and memory system that more than double the effective size of the installed main memory without significant added cost. This architecture is the first of its kind to employ real-time main-memory content compression at a performance competitive with the best the market has to offer. A large low-latency shared cache exists between the processor bus and a content-compressed main memory. Highspeed, low-latency hardware performs realtime compression and decompression of data traffic between the shared cache and the main memory. Sophisticated memory management hardware dynamically allocates main-memory storage in small sectors to accommodate storing the variable-sized compressed data without the need for "garbage" collection or significant wasted space due to fragmentation. Though the main-memory compression ratio is limited to the range 1:1-64:1, typical ratios range between 2:1 and 6:1, as measured in "real-world" system applications. Architecture Conventional "commodity" computer systems typically share a common architecture, in which a collection of processors are connected to a common SDRAM-based
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