[systemd-devel] [PATCH] systemd: add RDTCacheReservation= option to support CAT (Cache Allocation Technology)

[Lennart Poettering]

On Fri, 06.01.17 13:51, Marcelo Tosatti (mtosatti at redhat.com) wrote:

> > This really doesn't look pretty, neither the approach nor the
> > implementation...
> 
> Suggestions to improve the code or the approach are welcome.
> 
> > Is the option actually so complex that calling resctrltool is the only way
> > to adjust it? What about writing to the resctrlfs directly?
> 
> You'll have to deal with the issues that resctrltool deals with,
> namely:
> 
> 1) Filesystem locking.
> 2) Reading in every directory and the default 
> directory.
> 3) Converting the reservation request to proper sizes.
> 4) Converting:
> 		type=both --> type=data/type=code
> 
> 		type=data/type=code --> type=both
> 
> 4) Finding free space for the reservation.
> 5) Adjusting the default group reservation.
> 
> Since this steps must be performed by every user of
> CAT (including libvirt which plans to execute resctrltool
> as well), it was decided its better to maintain this logic
> in a centralized place.

Centralized place is fine, but please do this via a proper C library,
not some tool to shell out...

Hmm, if I see that correctly, then resctrltool is a python script? I
am particularly concerned about making systemd indirectly depend on
Python this way, in particular for something that isn't precisely a
core functionality of systemd.

Lennart

-- 
Lennart Poettering, Red Hat