Thread: [Under consideration] Remove 256MB limitation of the rootfs partition in the N900
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@SR is offline @SR
2010-02-10 , 12:31
Posts: 53 | Thanked: 143 times | Joined on Dec 2009 @ Russia
#53
Originally Posted by bitziz View Post
@SR, can you explain to me how to disable the watchdog on the device? you were saying you had considerable performance increase after disabling it?
No there was no actual performance increase. With original firmware you will not notice anything. The problem with watchdog was when I was mixing up file systems. When I disabled it performance was back to the level of original firmware.
If you still want to try disabling it you should use flasher with a command:
flasher-3.5 --set-rd-flags=no-omap-wd --set-rd-flags=no-ext-wd --enable-rd-mode

Originally Posted by stefanmohl View Post
@sr: I did see your previous post regarding aufs and unionfs. Great work in coming up with those results, even if the results themselves were kind of depressing! One thing I was wondering about though: If I got what you were doing right, you were using a ram disk backed by a flash drive; essentially your ram-disk was a write-through cache backed by the flash.

For the root partition problem, the situation is slightly different - both backing and front store are persistent. In this case, the fast flash stores the clean Nokia distro and the big flash stores all user additions. The big flash is superimposed over the fast flash so that reads see the big flash first, and writes only hit the big flash. This is more of a read-through rather than write-through scenario, if you get what I mean. I also assume that writes to files that already exist in the fast flash (i.e. modifications) go directly to the fast flash, rather than stick in the big flash like normal writes.

Do you think unionfs is so hopeless that there is no point in trying, or do you think you could have a look at how unionfs works in those conditions? Your basic idea is so pure and elegant that I really hope there is a way of saving it!

Does anyone here know anyone working on unionfs? Are there any Nokians here? Could Nokia consider putting in some work on unionfs?
No i was not using ram disk. I was mounting internal flash (the one with 256Mb) and ext3 partition on top of it (the 2Gb one from internal mmc or from external card, results were the same, swap on the card does not really slow down the system especially if swappiness is set to the lower setting, right now my system boots from mmc and everything works fast). While creating union both of them were mounted with writable rights.
The default behavior for the union is to write all modifications to the file to the most top writable partition that already has the file and to create new files in the most top writable partition that already has the closest folder structure. So generally that would be internal flash as it already has all files. ext3 partition is empty at the first boot.
Aufs has settings to override this behavior. For example it can be set to create all new files on the partition that has most free space. With this settings generally everything is written to the ext3 partition (and the existing files from internal flash are copied up to ext3 partition when they are modified).
I did not find how to change the default priorities in unionfs so most of the files end up in internal flash. I am not saying that it is hopeless. If i could override it so that all write and create operations were on the ext3 partition and only rename operations were in internal flash (as rename is the hardest operation for copy up and anyway it does not require space).