Re: /dev/shm

From: Marcin Dalecki (mdcki_at_gmx.net)
Date: 07/07/03

  • Next message: Marcin Dalecki: "Re: /dev/shm" 
    Date: Mon, 07 Jul 2003 02:48:41 +0200
To: dickey@herndon4.his.com

    Thomas Dickey wrote:
    > On Mon, Jul 07, 2003 at 01:58:19AM +0200, Marcin Dalecki wrote:
    >
    >>Myron J. Mayfield wrote:
    >>
    >>>I attempted to install the linux java sapgui on FreeBSD 5.0, but the jar
    >>>file only unpacked part of it. I then copied the files from my Redhat 9
    >>>machine. I linked up all the linux libraries needed and attempted to
    >>>start it. It gives me an error saying cant find /dev/shm. I tried
    >>>adding this to /dev but was unable to. Does anyone have any
    >>>information? Thank you. I am somewhat new to FreeBSD but have used
    >>>linux for Many years.
    >>
    >>For some unexcused reason there is the trend in Linux to represent
    >>everything as kind of a wired half finished pseudo file system. /proc pipe
    >>devicefs sysctl and so on... The list is really long. Even shared memmory is
    >>mapped to ehrm.... a filesystem. This is "expected" to be mounted at
    >>/dev/shm by the system. You can't expect FreeBSD to follow this path...
    >
    >
    > Linux isn't the only system that does this (learn a little, criticize less).

    There is a great span between everything and some things where it makes sense.
    Just please compare the devfs *implementations* between FreeBSD and Linux
    to see the difference.

    Some examples:

    /etc/rc.d/init.d# cat /proc/meminfo
             total: used: free: shared: buffers: cached:
    Mem: 526184448 515764224 10420224 0 43528192 353251328
    Swap: 536862720 0 536862720
    MemTotal: 513852 kB
    MemFree: 10176 kB
    MemShared: 0 kB
    Buffers: 42508 kB
    Cached: 344972 kB
    SwapCached: 0 kB
    Active: 332328 kB
    ActiveAnon: 79088 kB
    ActiveCache: 253240 kB
    Inact_dirty: 8932 kB
    Inact_laundry: 0 kB
    Inact_clean: 125308 kB
    Inact_target: 93312 kB
    HighTotal: 0 kB
    HighFree: 0 kB
    LowTotal: 513852 kB
    LowFree: 10176 kB
    SwapTotal: 524280 kB
    SwapFree: 524280 kB
    /etc/rc.d/init.d#

    Wonderfull well tought out conscise and dense design isn't it?

    Or maybe:
    /etc/rc.d/init.d# cat /proc/filesystems
    nodev rootfs
    nodev bdev
    nodev proc
    nodev sockfs
    nodev tmpfs
    nodev shm
    nodev pipefs
             ext2
    nodev ramfs
             iso9660
    nodev devpts
             ext3
    nodev usbdevfs
    nodev usbfs
    nodev binfmt_misc
    /etc/rc.d/init.d#

    And this is 2.4 kernel not the "upcomming" 2.6

    Oh and I know well about the motivation behing /dev/shm - the excuse is called
    "POSIX shm semantics". Which are broken in first place and never got over the
    "standard" draft state.

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