linux-kernel - Re: [PATCH v2 4/7] sched: Add pelt

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Message-ID: <da915e4d-07ce-2914-e090-0f8e3e9e9650@arm.com>
Date:   Mon, 13 May 2019 15:37:26 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Qais Yousef <qais.yousef@....com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Pavankumar Kondeti <pkondeti@...eaurora.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Uwe Kleine-Konig <u.kleine-koenig@...gutronix.de>,
        Quentin Perret <quentin.perret@....com>
Subject: Re: [PATCH v2 4/7] sched: Add pelt_rq tracepoint

On 5/13/19 2:48 PM, Qais Yousef wrote:
> On 05/13/19 14:14, Peter Zijlstra wrote:
>> On Fri, May 10, 2019 at 12:30:10PM +0100, Qais Yousef wrote:
>>
>>> +DECLARE_TRACE(pelt_rq,
>>> +	TP_PROTO(int cpu, const char *path, struct sched_avg *avg),
>>> +	TP_ARGS(cpu, path, avg));
>>> +
>>
>>> +static __always_inline void sched_trace_pelt_cfs_rq(struct cfs_rq *cfs_rq)
>>> +{
>>> +	if (trace_pelt_rq_enabled()) {
>>> +		int cpu = cpu_of(rq_of(cfs_rq));
>>> +		char path[SCHED_TP_PATH_LEN];
>>> +
>>> +		cfs_rq_tg_path(cfs_rq, path, SCHED_TP_PATH_LEN);
>>> +		trace_pelt_rq(cpu, path, &cfs_rq->avg);
>>> +	}
>>> +}
>>> +
>>> +static __always_inline void sched_trace_pelt_rt_rq(struct rq *rq)
>>> +{
>>> +	if (trace_pelt_rq_enabled()) {
>>> +		int cpu = cpu_of(rq);
>>> +
>>> +		trace_pelt_rq(cpu, NULL, &rq->avg_rt);
>>> +	}
>>> +}
>>> +
>>> +static __always_inline void sched_trace_pelt_dl_rq(struct rq *rq)
>>> +{
>>> +	if (trace_pelt_rq_enabled()) {
>>> +		int cpu = cpu_of(rq);
>>> +
>>> +		trace_pelt_rq(cpu, NULL, &rq->avg_dl);
>>> +	}
>>> +}
>>
>> Since it is only the one real tracepoint, how do we know which avg is
>> which?
> 
> Good question. I missed that to be honest since we are mainly interested in cfs
> and I was focused into not adding too many tracepoints..
> 
> I'm happy to create a tracepoint per class assuming that's what you're
> suggesting.

IMHO, you should also consider irq (rq->avg_irq), so when people are 
tracing asystem with 'IRQ' or 'paravirtual steal' time accounting, they 
will get the full picture.