On Fri, Jan 06, 2017 at 01:51:17PM -0200, Marcelo Tosatti wrote: > On Fri, Jan 06, 2017 at 05:26:36PM +0200, Mantas Mikulėnas wrote: > > On Fri, Jan 6, 2017 at 3:59 PM, Marcelo Tosatti <mtosa...@redhat.com> wrote: > > > > > > > > > > > Cache Allocation Technology is a feature on selected recent Intel Xeon > > > processors which allows control over L3 cache allocation. > > > > > > Kernel support has been merged to the upstream kernel, via a filesystem > > > resctrlfs. > > > > > > On top of that, a userspace utility, resctrltool has been written > > > to facilitate writing applications and using the filesystem > > > interface (see the rationale at > > > http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1300792.html). > > > > > > This patch adds a new option to systemd, RDTCacheReservation, > > > to allow configuration of CAT via resctrltool. > > > > > > See the first hunk of the patch for a description of the option > > > > > > 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.
Errr, no, that's not correct - Libvirt is certainly not going to spawn some python program to do this. If there's no C library API for this, libvirt will simply implement all the logic itself. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel