Re: [PATCH 05/12] x86/cqm,perf/core: Cgroup support prepare

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Jan 17, 2017 at 01:11:50PM +0100, Thomas Gleixner wrote:
> On Fri, 6 Jan 2017, Vikas Shivappa wrote:
> 
> > From: David Carrillo-Cisneros <davidcc@google.com>
> > 
> > cgroup hierarchy monitoring is not supported currently. This patch
> > builds all the necessary datastructures, cgroup APIs like alloc, free
> > etc and necessary quirks for supporting cgroup hierarchy monitoring in
> > later patches.
> > 
> > - Introduce a architecture specific data structure arch_info in
> > perf_cgroup to keep track of RMIDs and cgroup hierarchical monitoring.
> > - perf sched_in calls all the cgroup ancestors when a cgroup is
> > scheduled in. This will not work with cqm as we have a common per pkg
> > rmid associated with one task and hence cannot write different RMIds
> > into the MSR for each event. cqm driver enables a flag
> > PERF_EV_CGROUP_NO_RECURSION which indicates the perf to not call all
> > ancestor cgroups for each event and let the driver handle the hierarchy
> > monitoring for cgroup.
> > - Introduce event_terminate as event_destroy is called after cgrp is
> > disassociated from the event to support rmid handling of the cgroup.
> > This helps cqm clean up the cqm specific arch_info.
> > - Add the cgroup APIs for alloc,free,attach and can_attach
> > 
> > The above framework will be used to build different cgroup features in
> > later patches.
> 
> That's not a framework. It's a hodgepodge of core and x86 specific changes.

Trainwreck comes to mind. It completely fails to describe semantics of
the hacks and how they would preserve the cgroup invariants.