Date: Thu, 27 Aug 1998 12:20:14 -0400 (EDT) From: zhihuizhang <bf20761@binghamton.edu> To: hackers <freebsd-hackers@FreeBSD.ORG> Subject: FFS questions Message-ID: <Pine.SOL.L3.93.980827120824.10706A-100000@bingsun1>
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I am reading the source code in fs.h and the parameter fs_cpc confuses me. The comment says it is the number of cylinders per *cycle* in position table. What does the "cycle" mean? Basically the position table is used to space out contiguous logical blocks on the disk so that when the disk head moves to the next block, CPU has already initiates a new transfer request for exactly that block. But how can we measure the time it takes CPU (time-sharing by processes) to service an interrupt and initiate a new I/O? Is the disk always moving around at constant speed? When does the disk generate an interrupt? After it finish DMA a block or a sequence of contiguous blocks specified by the CPU's request? Any help is appreciated. -------------------------------------------------- | Zhihui Zhang, http://cs.binghamton.edu/~zzhang | | Dept. of Computer Science, SUNY at Binghamton | -------------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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