Changing default root filesystem to ext4

[Tixy]

On Wed, 2011-08-17 at 00:13 -0300, Ricardo Salveti wrote:
> Yeah, if we're doing this change it seems it would make more sense to
> jump directly to the btrfs, unless we can demonstrate that the
> performance is not that superior and have any kind of blocker issues.
>
> Do we have any kind of benchmark results comparing each filesystem
> when using them with SD cards around?

I'm doing some benchmarking, though it's mostly being aimed at producing
media access patterns to feed into a simulation tool. From these access
patterns, btrfs looks a lot worse than any ext file system.

I just looked at the timestamps of my blktrace logs to get some real
world timings. For untaring kernel source on one of my good performance
SD cards on a Beagleboard-xM takes:

	 m  s
ext4	 3:30
ext3	 8:30
ext2	 5:00
btrfs	13:40
nilfs	10:40
logfs	10:00

this is using default mount options for file system but with noatime.

These timings also bear out preliminary results from my simulation code.
Which I'm glad of :-)

Note, I've only been looking at write performance.

-- 
Tixy