Date: Fri, 19 Jul 1996 22:38:44 +0900 (KST) From: heo@cslsun10.sogang.ac.kr (Heo Sung Gwan) To: freebsd-fs@FreeBSD.ORG Subject: RE: RE:About buffer cache Message-ID: <9607191338.AA05500@cslsun10.sogang.ac.kr>
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I think that UNIX file system with buffer cache is not proper to support multimedia files(e.g mpeg files) becasue buffer cache is based on locality of referece(i.e. the recently referened block have high probabiliey to be referenced again). But multimedia files are accessed sequentially and therefore caching of the referenced block is not suitable and the block of mpeg file referenced by a process has low probability to be accessed by the other processes. So I think a FIFO buffer per each open file and the read-ahead to each FIFO buffer are good choice for multimedia file retrieval. In fact the many filesystems for multimedia adopted this approach( e.g. UC Berkeley CMFS). And there are two possible approaches: 1. Modification of buffer cache to FIFO buffers dynamically allocated. 2. User-level process that manages that FIFO buffers that access files through raw disk without buffer cache. Thanks for your resposes. Heo Sung-Gwan --- E-mail : heo@cslsun10.sogang.ac.kr
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