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From: Peter Zijlstra <peterz@infradead.org>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: mingo@redhat.com, mgorman@suse.de, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com,
	achaiken@aurora.tech, lkp@intel.com,
	linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Subject: Re: [PATCH v3 0/7] sched: support schedstats for RT sched class
Date: Tue, 31 Aug 2021 12:08:14 +0200	[thread overview]
Message-ID: <YS3/jhuRNS2GGVrp@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210824112946.9324-1-laoar.shao@gmail.com>

On Tue, Aug 24, 2021 at 11:29:39AM +0000, Yafang Shao wrote:
> Hi Ingo, Peter,
> 
> This feature is useful to trace the sched details of RT tasks. Hopefully
> you can give some feedback on it.
> 
> We want to measure the latency of RT tasks in our production
> environment with schedstats facility, but currently schedstats is only
> supported for fair sched class. In order to support if for other sched
> classes, we should make it independent of fair sched class. The struct
> sched_statistics is the schedular statistics of a task_struct or a
> task_group, both of which are independent of sched class. So we can move
> struct sched_statistics into struct task_struct and struct task_group to
> achieve the goal.

Do you really want schedstats or do you want the tracepoints? In general
I really want to cut back on the built-in statistics crud we carry,
there's too much and it seems to keep growing forever :-(

(as is the case here, you're extending it as well)

That said; making schedstats cover the other classes can be seen as
fixing an inconsistency, but then you forgot deadline.

> After the patchset, schestats are orgnized as follows,
> struct task_struct {
>     ...
>     struct sched_statistics statistics;
>     ...
>     struct sched_entity *se;
>     struct sched_rt_entity *rt;
>     ...
> };
> 
> struct task_group {                    |---> stats[0] : of CPU0
>     ...                                |
>     struct sched_statistics **stats; --|---> stats[1] : of CPU1
>     ...                                |
>                                        |---> stats[n] : of CPUn
>  #ifdef CONFIG_FAIR_GROUP_SCHED
>     struct sched_entity **se;
>  #endif
>  #ifdef CONFIG_RT_GROUP_SCHED
>     struct sched_rt_entity  **rt_se;
>  #endif
>     ...
> };

Yeah, this seems to give a terrible mess, let me see if I can come up
with anything less horrible.

  parent reply	other threads:[~2021-08-31 10:08 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24 11:29 Yafang Shao
2021-08-24 11:29 ` [PATCH v3 1/7] sched, fair: use __schedstat_set() in set_next_entity() Yafang Shao
2021-08-24 11:29 ` [PATCH v3 2/7] sched: make struct sched_statistics independent of fair sched class Yafang Shao
2021-08-31 10:14   ` Peter Zijlstra
2021-08-31 13:25     ` Yafang Shao
2021-08-31 10:19   ` Peter Zijlstra
2021-08-31 13:25     ` Yafang Shao
2021-08-24 11:29 ` [PATCH v3 3/7] sched: make schedstats helpers " Yafang Shao
2021-08-31 11:07   ` Peter Zijlstra
2021-08-31 13:27     ` Yafang Shao
2021-08-24 11:29 ` [PATCH v3 4/7] sched: make the output of schedstats " Yafang Shao
2021-08-31 11:08   ` Peter Zijlstra
2021-08-31 13:27     ` Yafang Shao
2021-08-24 11:29 ` [PATCH v3 5/7] sched: introduce task block time in schedstats Yafang Shao
2021-08-24 11:29 ` [PATCH v3 6/7] sched, rt: support sched_stat_runtime tracepoint for RT sched class Yafang Shao
2021-08-24 11:29 ` [PATCH v3 7/7] sched, rt: support schedstats " Yafang Shao
2021-08-31 10:08 ` Peter Zijlstra [this message]
2021-08-31 10:44   ` [PATCH v3 0/7] sched: " Peter Zijlstra
2021-08-31 13:21     ` Yafang Shao
2021-08-31 12:57   ` Yafang Shao

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