Date: Tue, 28 Mar 2017 09:56:22 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Juri Lelli <juri.lelli@arm.com>,
        Patrick Bellasi <patrick.bellasi@arm.com>
Subject: Re: [RFC PATCH 2/5] sched/events: Introduce cfs_rq load tracking
 trace event
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References: <20170328063541.12912-1-dietmar.eggemann@arm.com>
 <20170328063541.12912-3-dietmar.eggemann@arm.com>
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On Tue, Mar 28, 2017 at 07:35:38AM +0100, Dietmar Eggemann wrote:
> The trace event keys load and util (utilization) are mapped to:
> 
>  (1) load : cfs_rq->runnable_load_avg
> 
>  (2) util : cfs_rq->avg.util_avg
> 
> To let this trace event work for configurations w/ and w/o group
> scheduling support for cfs (CONFIG_FAIR_GROUP_SCHED) the following
> special handling is necessary for non-existent key=value pairs:
> 
>  path = "(null)" : In case of !CONFIG_FAIR_GROUP_SCHED.
> 
>  id   = -1       : In case of !CONFIG_FAIR_GROUP_SCHED.
> 
> The following list shows examples of the key=value pairs in different
> configurations for:
> 
>  (1) a root task_group:
> 
>      cpu=4 path=/ id=1 load=6 util=331

What's @id and why do we care?