[systemd-devel] [PATCH] readahead: read /usr files last for rotational media, skip /var

[Lennart Poettering]

On Fri, 30.09.11 16:52, Tom Gundersen (teg at jklm.no) wrote:

> 
> On Fri, Sep 30, 2011 at 4:26 PM, Paolo Bonzini <bonzini at gnu.org> wrote:
> > On 09/30/2011 03:39 PM, Kay Sievers wrote:
> >>
> >> Sure. I just think that this is not what we really want in the end.
> >
> > That I agree with, but good is the enemy of perfect...
> 
> How about this:
> 
> Rather than making the split between / and /usr, make it between
> Before and After basic.target (as basic.target is roughly what
> traditionally would require files to be on /). This would require us
> to associate files to be readahead with services, but based on what
> you wrote in a previous message that should be easy enough.
> 
> I guess that would give you roughly the same effect, but without
> relying on a split which is going away.
> 
> I still think that is far, far from perfect, but it might be a start
> (especially the association between files and services might turn into
> something very useful).

Any such logic in splitting the boot phase into two phases for read
ahead is very arbitrary I'd claim. Why just two phases, and why
precisely place the delimiter of the two phases at basic.target?

My earlier suggestion regarding doing a windowed location-based
reordering on top of a generally access time ordered list should be able
to make this much more flexible, and instead of two phases we'd have as
much as the compiled in window size allows.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.