Focusing on the problem that under workloads of large dataset
the performance of a Web server is dropped due to the disk I/O blockings
an application-controlled caching(ACC)approach is presented. In ACC
the cache tracking module traces the status of file caches in kernel according to the files access process of applications
and cache replacement and prefetch are performed incache control module to keep enough free space for file caches. With ACC
servers can control the file caches in user space
and determine whether a file is in caching
then schedule requests based on thisto improve the parallelism of the processor and disk I/O. Meanwhile
servers can choose a suitable policy of caching and prefetching to increase cache hit ratio. ACC is implemented in Flash server as a demonstration
in which pyramidal selection scheme is adopted. Experiments show thatthe performance of Flash with ACC can be largely enhanced under workloads of a large dataset. Even when the dataset load is slightly larger than the physical memory space
its throughput is improved by about 24.4%; when the dataset load is 2-3 times larger
the throughput improved by 3-4 times.
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references
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