From: "H. Peter Anvin" <hpa@zytor.com>
To: linux-kernel@vger.kernel.org
Subject: Re: Mounting a in-ROM filesystem efficiently
Date: 13 Dec 2001 12:38:28 -0800 [thread overview]
Message-ID: <9vb3k4$9kj$1@cesium.transmeta.com> (raw)
In-Reply-To: <20011213160007.D998D23CCB@persephone.dmz.logatique.fr>
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>
next prev parent reply other threads:[~2001-12-13 20:39 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-13 16:02 Mounting a in-ROM filesystem efficiently Thomas Capricelli
2001-12-13 16:22 ` Bradley D. LaRonde
2001-12-13 16:41 ` Thomas Capricelli
2001-12-13 17:10 ` Bradley D. LaRonde
2001-12-13 18:02 ` Richard B. Johnson
2001-12-13 18:14 ` Bradley D. LaRonde
2001-12-13 18:34 ` Richard B. Johnson
2001-12-13 18:52 ` Bradley D. LaRonde
2001-12-13 19:41 ` Richard B. Johnson
2001-12-13 20:09 ` Bradley D. LaRonde
[not found] ` <08d701c18412/mnt/tmp/sendmee91d2c0601010a@prefect>
2001-12-18 1:27 ` Pavel Machek
2001-12-14 11:03 ` Catalin Marinas
2001-12-13 17:49 ` David Woodhouse
2001-12-13 18:06 ` Bradley D. LaRonde
2001-12-13 20:38 ` H. Peter Anvin [this message]
2001-12-13 20:52 ` Bradley D. LaRonde
2001-12-14 9:45 ` David Woodhouse
2001-12-14 15:27 ` Bradley D. LaRonde
2001-12-14 16:51 ` David Woodhouse
2001-12-14 17:02 ` Bradley D. LaRonde
2001-12-14 17:03 ` David Woodhouse
2001-12-14 17:12 ` Bradley D. LaRonde
2001-12-14 17:16 ` David Woodhouse
2001-12-14 17:27 ` Bradley D. LaRonde
2001-12-16 9:51 ` Christoph Rohland
2002-01-23 8:01 ` Eric W. Biederman
[not found] <20011214072540.D7457@duron.intern.kubla.de>
2001-12-17 13:24 ` Richard B. Johnson
2001-12-18 12:10 ` Helge Hafting
2001-12-18 14:00 ` Richard B. Johnson
2001-12-18 14:09 ` Alan Cox
2001-12-18 15:21 ` Mr. James W. Laferriere
2001-12-18 20:56 ` H. Peter Anvin
2001-12-18 16:27 ` Kent Borg
2001-12-18 17:05 ` Herman Oosthuysen
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