linux-kernel - Re: [PATCH v8 2/3] sched/fair: update scale invariance of PELT

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Message-ID: <308e0dcc-f406-77b5-5631-d00dd4680a7d@arm.com>
Date:   Wed, 23 Jan 2019 12:19:40 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Paul Turner <pjt@...gle.com>, Ben Segall <bsegall@...gle.com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        pkondeti@...eaurora.org, Quentin Perret <quentin.perret@....com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v8 2/3] sched/fair: update scale invariance of PELT

On 1/23/19 10:48 AM, Vincent Guittot wrote:
> On Wed, 23 Jan 2019 at 09:26, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
>>
>> On 1/16/19 10:43 AM, Vincent Guittot wrote:
>>
>> [...]
>>
>>> +static inline u64 rq_clock_pelt(struct rq *rq)
>>> +{
>>
>> Doesn't this function need
>>
>>     lockdep_assert_held(&rq->lock);
>>     assert_clock_updated(rq);
> 
> originally, it was replacing cfs_rq_clock_task which doesn't have this
> debugging code.
> But it also replaces rq_clock_task for deadline and rt so it's
> probably worthing adding them for such case

I think so. Moreover, cfs_rq_clock_pelt() uses rq_clock_pelt(). Like 
cfs_rq_clock_task(), which was replaced by cfs_rq_clock_pelt() in 
fair.c, uses rq_clock_task().

>> like rq_clock() and rq_clock_task()? Later to support commit
>> cb42c9a3ebbb "sched/core: Add debugging code to catch missing
>> update_rq_clock() calls".
>>
>>> +     return rq->clock_pelt - rq->lost_idle_time;
>>> +}
>>
>> [...]