[systemd-devel] [PATCH] [RFC][PLEASE TEST] readahead: chunk on spinning media

[Lennart Poettering]

On Fri, 22.03.13 15:22, Auke Kok (auke-jan.h.kok at intel.com) wrote:

Heya,

Hmm, it would be interesting to know how much data we actually read at
boot. This information should actually be easy to determine, since we
run mincore() anyway... With that information, and a rough idea how fast
harddisks are when reading linearly (mine does 200MB/s, so let's say
conservatively 50MB/s), we have a rough idea how fast we ever could be. 

Then, I generally believe better than trying to be smart when reading
things we should much rather try to place things properly on disk. We
already defrag things based on the read order for btrfs, we should do
the same for ext4. The API for that unfortunately awful, but e4rat has
shown that this does work. Basically, this is what you do:

https://lwn.net/Articles/334531/

And I am pretty sure that should be the focus here really.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.