[OE-core] wic creates ext4 images that read really slow in u-boot

[Mike Looijmans]

>>> I am aware of two fixes for U-Boot. I will look them up, and reply again to this thread.

Browsing through u-boot commits, I found this gem that's disabled by default:

CONFIG_BLOCK_CACHE=y

The commit is this one:

commit e40cf34a29f1b248643731a11fb1c6f0520d016c
Author: Eric Nelson <eric at nelint.com>
Date:   Mon Mar 28 10:05:44 2016 -0700

     drivers: block: add block device cache

     Add a block device cache to speed up repeated reads of block devices by
     various filesystems.

     This small amount of cache can dramatically speed up filesystem
     operations by skipping repeated reads of common areas of a block
     device (typically directory structures).

     This has shown to have some benefit on FAT filesystem operations of
     loading a kernel and RAM disk, but more dramatic benefits on ext4
     filesystems when the kernel and/or RAM disk are spread across
     multiple extent header structures as described in commit fc0fc50.
...

I'll be giving that a test drive soon...