The existing policy sets dirty_background_bytes to 5, which is erroneously
too small that incurs write amplification and read starvations.
Considering a raspi with 2 GiB of RAM, this is 43 million times smaller
than the default Linux policy, which is 10%.
Considering that this will be deployed to mostly read-only system with
emphasis on data integrity (hence needing tighter data writeback), set
this to 256 KiB.
Continuing addressing the overly excessive data writeback policies, also
bump the dirty_writeback_centisecs from 250ms to 1000ms. Any dirty data
written in the past 1 second will be written to the storage.
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
