mount time (was Re: Fwd: Hello -- NAND/NOR Flash design for GTA02)
andy at openmoko.com
Fri Jan 11 16:35:57 CET 2008
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Somebody in the thread at some point said:
> - make the partition we have to scan smaller
> - distinct partitions (Andy)
> - initramfs
This will need unpacking / regenerating when packages want to stick
things in there, really we need most of the stuff initscripts want to
touch available quickly so this will be large too, also cause a blocking
delay while the large fs image is fetched from NAND and unpacked.
> - overlay (Joachim, OpenWRT uses squashfs+jffs2)
Didn't find anything on Joachim in Google. There's unionfs as well in
the overlay side, not sure it's in mainline.
> - as a variation of the above, separate read-only data from read-write
> data - only the latter needs scanning (that's from OpenWRT again)
Hey that's pretty good, having a ro /usr is not so uncommon, we can
mount -oremount,rw when we do a package change.
> - do not do a linear scan of everything
> - checkpointing (yaffs2)
> - better data structures (LogFS)
I guess we would take a gamble if we chose LogFS, there is limited time
to gain experience with it but I guess it can be possible.
> - accelerate the speed at which we do the linear scan
> - make NAND access faster (hwecc, DMA, readahead)
> - skip blocks we know can't contain meta-data (*)
> - access the file system before the scan completes (*)
Hey what happens if you mounted the root filesystem ro, did the whole
initscripts without a writable /? Would it come up immediately and then
you can start mounting rw at a mountpoint, pivot the rw one on top of
the ro one when it is done?
> Anyway, there's more to examine, and I need to gather a bit more
> background data as well. I rather like the idea behind LogFS, because
Yep, thanks for the update!
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