lkml.org 
[lkml]   [2001]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: Mounting a in-ROM filesystem efficiently
    Date
    Followup to:  <20011213160007.D998D23CCB@persephone.dmz.logatique.fr>
    By author: Thomas Capricelli <orzel@kde.org>
    In newsgroup: linux.dev.kernel
    >
    > Hello,
    >
    > I'm looking for a way to put a filesystem into ROM.
    > Seems pretty trivial, isn't it ?
    >
    > My understanding is (the way initrd does, and the way I do as of today)
    > * create a RAMDISK
    > * loads the data into ramdisk
    > * mount the ramdisk
    >
    > problem is that I don't want to waste the RAM as the data in the ROM is
    > already in the address space. (it's an embedded system, btw)
    >
    > Speed is not an issue here. ROM access might be slower than RAM, it will
    > always be so much quicker than a disk access. (wrong?)
    >

    Frequently wrong. Depending on the interface, ROM can be just
    unbelievably slow.

    > Ideally, i would give address/length of the fs in ROM to a function, and I
    > would get a ramdisk configured to read its data exactly there, and not in
    > ram.

    The right thing for you to do is to write a block device driver, and
    then mount that block device like any order device. Your in-use data
    will be copied to RAM (i.e. cached), but it can be dropped and
    re-fetched as necessary. This should be the desired behaviour.

    -hpa
    --
    <hpa@transmeta.com> at work, <hpa@zytor.com> in private!
    "Unix gives you enough rope to shoot yourself in the foot."
    http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:14    [W:0.047 / U:29.092 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site