logcatd: fallocate and fadvise to logcat files

1. Pinning and fallocating blocks can avoid filesystem fragmentation.
2. Dropping caches can avoid memory pressure.
3. Use 2MB files

Bug: 136483670
Bug: 137180754
Change-Id: I0827bd903a677cbcbf3688983e847301cd541cdd
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
2 files changed