• Unix file system, extensions

    November 18, 2012

    There has been many advances in file systems since ext2 was introduced in 1992, and especially since the unix file system, on which much of ext2 is based, as introduced in 1969. We look at extended attributes, a new permission model with Access Control Lists (ACLS), Hash Trees, Snapshots and Journaling. Extended attributes The inode [...]

  • Unix file system, part 2

    November 16, 2012

    Directories The unix directory gives names to inodes. Each directory is a listing of name-inode pairs. A pair generates a hard link to the inode structure, and a count of the number of such pairs is kept in the inode as the link count. (The ls command has options to show both the link count [...]

  • Unix file system

    November 16, 2012

    The unix file system of the very first unix system is still the basis of the default file systems for Linux, FreeBSD, and possibly many other unix forks. We will talk mostly about the classic unix file system, is which very similar to ext2, ext3 or ext4 — the file systems of a default Linux [...]

  • Page frame management and the swap cache

    November 2, 2012

    Along with the data structure of the page table, the kernel keeps a data structure which describes physical memory. Each page frame has an entry in the data structure. The entry keeps track of whether the page frame is in use or free, and also information about the sharing status of the page frame. Page [...]

  • Virtual Memory: demand and eviction

    November 1, 2012

    Only those pages where there are reads or writes to addresses contained in the page will be allocated page frames of physical memory. Of the various techniques to determine which pages are required, the most straight-forward is demand paged virtual memory. Demand paging will assign a page frame in reaction to the processor demanding a [...]

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