[lkml]   [2000]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: Do ramdisk exec's map direct to buffer cache?
    In article <>,
    David Woodhouse <> wrote:
    >My current inclination is to make CONFIG_BLK_DEV a config option, turn it
    >off to save space, and use JFFS directly on flash chips, with ramfs for /tmp
    >and possibly also /var
    >I'm fairly sure that ramfs does share pages as you'd hope it does.

    ramfs does indeed share pages, and does more than that: it shares the
    directory structure with the directory cache directly, so there is not
    any wasted memory even in meta-data. That was one of the design goals
    (along with extreme simplicity - it's the smallest and fastest
    filesystem around).

    That said, ramfs isn't perfect. It's not a "tmpfs" in that it cannot
    page anything out to disk (a non-issue in embedded devices, but it would
    make ramfs more useful in general use), and it's new code that isn't
    used by all that many people - so it could have (and has had) problems.
    As 99% of the functionality of ramfs is actually just using VFS code
    directly the basics of ramfs are very solid, but the devil is in the

    If you want to pre-populate ramfs (the way initrd does the old-style
    ramdisk), I would suggest using a compressed tar-file approach. In the
    long run I definitely want to get rid of the old-style ramdisk, as it
    has some serious problems both from a design standpoint and from a
    maintenance angle (the mm games it plays are much worse than the simple
    page-pinning stuff that ramfs can do - ramfs plays at a much higher
    level and has access to better abstractions through that).

    The only problem with JFFS is that it doesn't do compression, so there's
    a lot to be said for using cramfs if you have space constraints (and in
    embedded devices, if you don't have space constraints you're doing
    something wrong ;). So mixture of ramfs, cramfs and JFFS can be a good


    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:57    [W:0.019 / U:0.876 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site