[systemd-devel] readhead - systemd vs. readahead

[Lennart Poettering]

On Fri, 08.10.10 23:49, Andrey Borzenkov (arvidjaar at mail.ru) wrote:

> It seems that readahead sources already include systemd unit
> configuration. I have readahead 1.5.7 and have here:
> 
> /lib/systemd/system/default.target.wants/readahead-collect.service
> /lib/systemd/system/default.target.wants/readahead-replay.service
> /lib/systemd/system/readahead-collect.service
> /lib/systemd/system/readahead-replay.service
> /lib/systemd/system/readahead-sort.service
> 
> What is relation of readahead services and systemd services? From
> names they seem to be identical.

The systemd suite includes its own minimal readahead implementation now
which takes the best ideas from the existing implementions (and there
are way too many) and adds a couple of new ideas on top and the result
should be something that should actually be something that is worth
supporting. It does not require kernel patches, it does not conflict
with auditing, it allows running data collection and replay at the same
time. 

That said it is not optimized to the last bit yet, and there are a
number of features we still need to add. However, it has a number of
fancy features (such as btrfs defrag support) that so far have been seen
only in special-purpose and toy read-ahead implementations.

Or in other words: this implementation is the result of studying what we
had so far and then destilling something out of it that we can ship on
general purposes distros enabled by default. It is reasonably complete
but still work in progress.

To enable this, use:

systemctl enable systemd-readahead-collect.service systemd-readahead-replay.service

Lennart

-- 
Lennart Poettering - Red Hat, Inc.