On Sun, 2008-04-20 at 17:04 +0100, Jamie Lokier wrote: > Josh Boyer wrote: > > > Is it even a good idea? The UBI (version 1 :-) initial scan is not > > > fast for large flash, and if the bootloader does it too, that's twice > > > as much time to boot. > > > > It's a good idea, yes. Particularly if you want to boot from NAND > > flash. > > > > Can you define "large device"? It only scans the first 1 or 2 pages for > > each eraseblock to build up the volume tables. That really isn't that > > slow... > > I was thinking this: > > Hamish Moffatt wrote (Message-ID: <[EMAIL PROTECTED]>): > > Sorry I should've said 512MiB perhaps: 512 megabytes. > > UBI attach time appears to be about 6 seconds. > > If 6 seconds is as fast as it can be done, annoying but fair enough.
You should read that thread a bit more carefully. The scan time is highly dependent upon the NAND driver beneath UBI. For example, a UBI scan/attach on a 1GiB device on OLPC was 2 seconds. > > Adding _another_ 6 seconds to the boot time seems a lot to me. You mean adding another "X amount of time depending on factors outside of UBI's control." > The only ways I see to improve the speed in general are: > > 1. Partition the NAND into multiple independent UBIs, so the boot > loader doesn't have the scan the whole chip, but that is > obviously not so good for wear levelling. (It's probably > alright, though, if it's like the /boot partition on a standard > Linux distro - not updated very often.) > > 2. Change UBI's data structure so that the number of pages it needs > to read is a sub-linear function of the number of erase blocks. > I think this is what's meant by 'UBI 2'. > > To remove the double scan: > > > > However, if there was a protocol for bootloader to pass the scan > > > results to the booted kernel, that would be very nice. > > > > Maybe. I was never fully convinced of that. > > I can understand the hesitation, but I think 6 seconds just to find > the kernel - especially when doing a 'disk resume' - is quite a lot. You should really stop quoting this 6 second number. Anyway, passing the scan results from a bootloader becomes very involved. You have to store it somewhere, probably preserving a section of DRAM, which isn't always easy. > Note that I haven't tried UBI myself yet. I'm going on what has been > written to the list so far, as quoted above. Maybe you should try it :). josh ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ U-Boot-Users mailing list U-Boot-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/u-boot-users
