[Vibrant Android Development] djkdawg:
Frequently Asked Questions

Q: My apps are force closing while this fix is running, and I can't use my phone!

A: By design. The script has backed up/copied your apps over to the internal SD card (remember the requirement about 1.5GB of free space on the SD card?). It is now overwriting them with a 1.5GB file. As the file overwrites an app that is trying to do something, it will probably force close. This is normal.

Closing all running apps, and removing widgets before running this fix can make the process much smoother, though.

Q: The script can't transfer files to my phone / The script can't run / Help help I'm dieing!

A: Read the first post again.

Q: My paid apps from the market don't show up.

A: I will hopefully have a fix for this sooner or later. Hold tight! It's in the known issues. I don't have access to paid apps, so I can't test this.

Q: Does this need busybox?

A: No, busybox is included.

Q: I only have 200mb of free space now! What gives?

A: The lag fix has made a 1.5GB file, and is storing all of the data inside there. The side effect is that the free space meter is now incorrect. Sorry, this can't be helped.

You can check real free space by using ADB like this:

Code:

adb shell

su

busybox df -h

Q: When I use a backup tool, the backup is now 1.5GB big! It's taking forever!

A: The backup tool isn't designed to work with this fix. It will work, it just won't work well. Hopefully this fix will be short lived, and either Samsung will give us a new update, or someone will give us a good custom firmware that can natively mount what we need, where we need it. Or someone might come out with a better backup manager. Until then, we suffer.

Q: Will a reflash wipe this fix?

A: Yes, a reflash will wipe everything this fix did.

Q: Can this brick my phone?

A: If you know how to get to the download mode from power off (hint: volumedown+home+power), then almost nothing short of throwing your phone off a tall building can actually brick it. If you can't do this though, or don't know someone who can, then you're better off waiting for samsung to release a fix. Anything that moves files around on your device has the potential to break things, and this fix has no QA department.

Q: Why is /dbdata not included in your fix, but other people have included it?

A: Other people have included it in the same way my 2-2 fix includes it. However, /dbdata is ROM backed. This means that the real files are on ROM, and only the changes appear in the /dbdata folder. When copying or moving files from this folder, you would need to specify each folder by exact name to ensure that it was copied across, and each firmware can have their own names. (This is because RFS wildcard will not catch an unused ROM backed file.) In some cases, you can get lucky and have this work perfectly because you have already used all the files in /dbdata. There is no fail safe method to do this though, and /dbdata does not make a big difference to performance. (It is already on NAND flash.) If you want to try your luck, v2-2 is still available.

Q: Why does this lag fix work? Is it slowly destroying my phone?

A: Let's say an application counts from 1 to 10, and writes the value each time to disk.

Stock:

1 -> App tells RFS to write 1 to disk -> RFS writes 1 to disk -> RFS writes journal saying to changed the value on the disk.

2 -> App tells RFS to write 2 to disk -> RFS writes 2 to disk -> RFS writes journal saying to changed the value on the disk.

..

9 -> App tells RFS to write 9 to disk -> RFS writes 9 to disk -> RFS writes journal saying to changed the value on the disk.

10 -> App tells RFS to write 10 to disk -> RFS writes 10 to disk -> RFS writes journal saying it changed the value on the disk.

Total physical disk writes: 20. Speed: SLOW! Wear and tear on disk: HIGH!

Lag Fix:

1 -> App tells EXT2 to write 1 to disk -> EXT2 stores 1 in RAM.

2 -> App tells EXT2 to write 2 to disk -> EXT2 stores 2 in RAM.

..

9 -> App tells EXT2 to write 9 to disk -> EXT2 stores 9 in RAM.

10 -> App tells EXT2 to write 10 to disk -> EXT2 stores 10 in RAM.

..

EXT2 tells RFS to write 10 to disk -> RFS writes 10 to disk -> RFS writes journal saying it changed the value on the disk.

Total physical disk writes: 2. Speed: FAST! Wear and tear on disk: LOW!

This isn't exactly what is happening, but it gives you the general idea.

Q: Can this mod work on other Android devices? Would we see a performance boost on them as well? If not why is it limited to the Galaxy S?

A: SGS has very very good hardware, but it has some parts of it's hardware poorly implemented. The filesystem that samsung chose to use is custom-built using FAT32 as a base, RFS. It has a lot of the problems that FAT32 has, and should have been left back in the 90s, or even the 80s.

One of the big issues with it is how it handles multiple requests - it blocks. It blocks everything. When your mail app wants to read the mail you just tried to view, but your twitter app is busy writing a new tweat it just received, your mail app is forced to wait.

This is bad, but it could be worse! And it is... your twitter app didn't just get one tweat, it got 50 tweaks. It is busy writing the tweats one by one to the filesystem. This would be fine, since all modern filesystems will buffer writes, so instead of writing each one at a time, they will batch them together and write it as a big chunk. Uh oh - RFS does no buffering at all! After each write, it will also write an update to the grafted-on journal system. Guess what happened to your mail you were trying to view while all this happened? It 'lagged' and you got a black screen for half a second, before the mail popped into view.

Luckily the hardware on the device is so good that you usually don't even notice the problem until you have a lot of apps running, all writing their updates when you unlock the phone.

This is mostly speculation based on experiments done on RFS -- RFS is closed source, and we have no idea if the problems are just badly set settings (such as a block size that is too small), coding bugs in the implementation, or if RFS is just really that badly designed.

This fix just grafts a buffer on top of the RFS filesystem, using a very very simple and fast filesystem, EXT2. It fixes most of the issues by writing to RFS as seldom as possible.

So no, this fix won't fix other devices, since they're already running quite close to maximum speed. The SGS at stock is running nowhere near maximum speed, and this lag fix takes it a bit closer. You could probably speed up other devices by tweaking the filesystem settings to give them a big buffer or similar, but it isn't really needed. (I haven't actually tried to put an EXT2 onto any other Android phone, as I don't have any other Android phone, so this is just speculation.)

Q: My phone is fast now!

A: Yeah.

Last edited by RyanZA; 18th August 2010 at 10:52 PM..