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

Paolo Bonzini bonzini at gnu.org
Fri Sep 30 06:25:10 PDT 2011

On 09/30/2011 03:08 PM, Kay Sievers wrote:
> You did not read any of the pages behind the links in the earlier
> mail, right?:)

Gotcha. :)

>>> >>  Rules which files to prioritize *might* make sense, sorting by
>>> >>  top-level dir doesn't really.
> Nah, I meant something different. Your hardcoded /usr is a rule too.
> It's not about specific file names to prioritizr but you could have a
> set of rules that can be provided that could say: "prioritize
> */lib/modules/* over the rest", and things like that.

I'm not sure that would be good anyway.  You need to prioritize by boot 
phases, not by files.  There's nothing special in /lib/modules, it's 
just that *some of its contents* are needed earlier that 
/usr/sbin/NetworkManager.  But ipt_MASQUERADE.ko is needed later than 
say drivers/net/e1000e/e1000e.ko.

> /usr will not be a good rule, and hard coding such things in the code,
> we should should probably avoid in general.

That's what comments and TODO are for.

Even if it will not be a good rule, right now it is at least decent, and 
right now systemd-readahead is a pretty bad readahead for rotational 
media (still the majority).  Did you see the numbers I gave?


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