[systemd-devel] [RFC PATCH] Add rdt/resctrl support in systemd

[Daniel P. Berrangé]

On Fri, Jun 08, 2018 at 01:47:28PM +0200, Lennart Poettering wrote:
> On Fr, 08.06.18 17:54, Zhangyanfei (YF) (yanfei.zhang at huawei.com) wrote:
> 
> > Hello
> > 
> > The linux kernel has support all Intel RDT(Resource Director Technology)[1] features,
> > via a filesystem resctrlfs [2].
> > Libvirt has introduced CAT into it snice v4.1.0 [3].And Marcelo tried to post a
> > patch to add CAT support into systemd before but the way the patch did (gluing a python tool)
> > is not acceptable by the maintainer [4].
> > 
> > I think including RDT support in systemd is necessary because we should have a
> > central place to control how we use the RDT features. We should have a global control
> > over the resctrlfs when applications in the system want to use RDT.
> > 
> > My initial idea is:
> > 1. resctrlfs should be mounted/unmounted in systemd just like
> > cgroupfs.
> 
> sounds fine to me
> 
> though this does make me wonder: what's the reason this stuff is not
> exposed via cgroups anyway? why is this form of resource management
> separate from cgroups resource mgmt?
> 
> > 2. Systemd should lock/unlock resctrlfs when ncessary to avoid
> > contending.
> 
> what do you mean by lock/unlock?
> 
> Note that i have no understanding of RDT whatsoever, hence if
> "lock"/"unlock" is some RDT term in this context, please elaborate.

It'll be referring to the suggestion from the kernel docs that every
app use flock() to avoid races on the files being changed. See approx
line 520 in:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/x86/intel_rdt_ui.txt

Regards,
Daniel
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