In this thread, people say that readahead
increases performance of sequential reads from the SD card.
This LWN article also suggests that readahead
is a key feature to boost boot times, even on very fast media such as SSDs. This is because the normal boot sequence has a lot of "holes" (in term of CPU usage) waiting for things to be ready (just think at udev
populating /dev
directory, etc.). These "holes" can be used by readahead
to prefetch disk sectors that will be used later in the boot sequence, thus skipping blocking I/O requests.