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

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Message-ID: <20170117123132.GB6485@twins.programming.kicks-ass.net>
Date:   Tue, 17 Jan 2017 13:31:32 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        vikas.shivappa@...el.com, davidcc@...gle.com, eranian@...gle.com,
        linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        mingo@...nel.org, ravi.v.shankar@...el.com, tony.luck@...el.com,
        fenghua.yu@...el.com, andi.kleen@...el.com, h.peter.anvin@...el.com
Subject: Re: [PATCH 05/12] x86/cqm,perf/core: Cgroup support prepare

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@...gle.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.