[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <48c178fc-108f-382b-e054-83e88ef9b01b@arm.com>
Date: Thu, 10 Nov 2022 15:59:01 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Kajetan Puchalski <kajetan.puchalski@....com>,
Jian-Min Liu <jian-min.liu@...iatek.com>,
Ingo Molnar <mingo@...nel.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Morten Rasmussen <morten.rasmussen@....com>,
Vincent Donnefort <vdonnefort@...gle.com>,
Quentin Perret <qperret@...gle.com>,
Patrick Bellasi <patrick.bellasi@...bug.net>,
Abhijeet Dharmapurikar <adharmap@...cinc.com>,
Qais Yousef <qais.yousef@....com>,
linux-kernel@...r.kernel.org,
Jonathan JMChen <jonathan.jmchen@...iatek.com>
Subject: Re: [RFC PATCH 0/1] sched/pelt: Change PELT halflife at runtime
On 10/11/2022 14:05, Peter Zijlstra wrote:
> On Thu, Nov 10, 2022 at 12:16:26PM +0100, Dietmar Eggemann wrote:
>> On 07/11/2022 14:41, Peter Zijlstra wrote:
>>> On Thu, Sep 29, 2022 at 03:41:47PM +0100, Kajetan Puchalski wrote:
>>
>> [...]
>>
>>> @@ -2956,13 +2958,26 @@ static inline unsigned long cpu_util_dl(struct rq *rq)
>>> */
>>> static inline unsigned long cpu_util_cfs(int cpu)
>>> {
>>> + struct rq *rq = cpu_rq(cpu);
>>> struct cfs_rq *cfs_rq;
>>> unsigned long util;
>>>
>>> - cfs_rq = &cpu_rq(cpu)->cfs;
>>> + cfs_rq = &rq->cfs;
>>> util = READ_ONCE(cfs_rq->avg.util_avg);
>>>
>>> if (sched_feat(UTIL_EST)) {
>>> + if (sched_feat(UTIL_EST_FASTER)) {
>>> + struct task_struct *curr;
>>> +
>>> + rcu_read_lock();
>>> + curr = rcu_dereference(rq->curr);
>>> + if (likely(curr->sched_class == &fair_sched_class)) {
>>> + u64 runtime = curr->se.sum_exec_runtime - curr->se.exec_start;
>>
>> Don't we and up with gigantic runtime numbers here?
>>
>> oot@...o:~# cat /proc/1676/task/1676/schedstat
>> 36946300 1150620 11
>> root@...o:~# cat /proc/1676/task/1676/sched
>> rt-app (1676, #threads: 2)
>> -------------------------------------------------------------------
>> se.exec_start : 77766.964240 <- !
>> se.vruntime : 563.587883
>> e.sum_exec_runtime : 36.946300 <- !
>> se.nr_migrations : 0
>> ...
>>
>> I expect cpu_util_cfs() to be ~1024 almost all the time now.
>
> Duh, obviously I meant to measure the runtime of the current activation
> and messed up.
>
> We don't appear to have the right information to compute this atm :/
This would be:
u64 now = rq_clock_task(rq);
u64 runtime = now - curr->se.exec_start;
but we don't hold the rq lock so we can't get `now`?
Powered by blists - more mailing lists