loading the kernel and root FS separately from flash?
Wolfgang Denk
wd at denx.de
Mon Jun 28 20:41:54 EST 2004
In message <Pine.LNX.4.60.0406280600140.3259 at localhost.localdomain> you wrote:
>
> i suspect that leaving my root filesystem in flash would cause
> noticeable performance problems (even if i managed to structure it so
What makes you think so?
The startup behaviour may change: at the moment you load the whole
root filesystem into RAM before you can run anything at all - that
means it takes longer before the first application can start. But
then everything _is_ in RAM, so anything else will start quickly,
too.
With a flash based root filesystem only the things (binaries,
libraries) that are actually needed for the first user processes
(init etc.) will be loaded to RAM, so they may actually start faster
than from a RAM disk. But anything else may require to load
additional libraries etc. so it may start slower than from a ramdisk.
On the other hand, some code or binaries (like error handling stuff,
debug tools etc.) may not be loaded at all for normal operation, so
you will have more RAM free, which adds to speed, too.
> that it could be read-only). how hard would it be to automatically
> have that root FS copied from JFFS2 to RAM and mounted from there?
This makes just no sense to me.
> can that be done as a kernel option i haven't seen? or do i have to
> do that manually, involving something like "pivot_root"? or is it
> worth the trouble?
I cannot see any advantages from such a setup.
If you want a RAM based root filesystem, use a ramdisk.
Best regards,
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
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