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Silly Window Syndrome is a type of communications system thrashing. OVERVIEW In modern computers, thrashing may occur in the Paging system (if there is not 'sufficient' physical memory or the disk access time is overly long), or in the communications system (especially in conflicts over internal bus access), etc. Depending on the configuration and algorithms involved, the '' Throughput '' and '' Latency '' of a system may degrade by multiple Orders Of Magnitude . In of a program or a workload cannot be effectively held within physical memory, then constant data swapping, i.e., thrashing, may occur. The term was first used during the tape operating system days to describe the sound the tapes made when data was being rapidly written to and read from them. Many older low-end computers have insufficient RAM (memory) for modern usage patterns and increasing the amount of memory can often cause the computer to run noticeably faster. This speed increase is due to removing the need for paging. An example of this sort of situation occurred on the IBM System/360 series Mainframe Computer , in which a particular instruction could consist of an execute instruction, which crosses a Page boundary, that the instruction points to a move instruction, that itself also crosses a page boundary, targeting a move of data from a source that crosses a page boundary, to a target of data that also crosses a page boundary. The total amount of pages thus being used by this particular instruction is eight, and all eight pages must be present in memory at the same time. If the operating system will allocate less than eight pages of actual memory in this example, when it attempts to swap out some part of the instruction or data to bring in the remainder, the instruction will again Page Fault , and it will thrash on every attempt to restart the failing instruction. To resolve thrashing due to excessive paging, a user can do any of the following. #Increase the amount of RAM in the computer (generally the best long-term solution). #Decrease the number of programs being run on the computer. #Adjust the size of the swap file. The term is also used when a small set of faster storage space, intended to be used to speed up access to a larger set of slower storage space, is accessed in a way that cancels out any benefits from the faster storage. An example of this is cache thrashing, where main memory is accessed in a pattern that leads to multiple main memory locations competing for the same cache lines, resulting in excessive Cache Misses . This is most problematic for caches that have low Associativity . REFERENCES
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