linux-kernel - Re: [CFS Bandwidth Control v4 6/7] sched: hierarchical task accounting for SCHED

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Message-ID: <4D646AC0.7030809@jp.fujitsu.com>
Date:	Wed, 23 Feb 2011 11:02:40 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Paul Turner <pjt@...gle.com>
CC:	linux-kernel@...r.kernel.org,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Avi Kivity <avi@...hat.com>,
	Chris Friesen <cfriesen@...tel.com>
Subject: Re: [CFS Bandwidth Control v4 6/7] sched: hierarchical task accounting
 for SCHED_OTHER

(2011/02/16 12:18), Paul Turner wrote:
> @@ -1428,6 +1464,7 @@ enqueue_task_fair(struct rq *rq, struct 
>  		update_cfs_shares(cfs_rq);
>  	}
>  
> +	account_hier_tasks(&p->se, 1);
>  	hrtick_update(rq);
>  }
>  
> @@ -1461,6 +1498,7 @@ static void dequeue_task_fair(struct rq 
>  		update_cfs_shares(cfs_rq);
>  	}
>  
> +	account_hier_tasks(&p->se, -1);
>  	hrtick_update(rq);
>  }
>  

Why hrtick_update() is need to be delayed after modifying nr_running? 
You should not impact current hrtick logic without once mentioning.

> Index: tip/kernel/sched_rt.c
> ===================================================================
> --- tip.orig/kernel/sched_rt.c
> +++ tip/kernel/sched_rt.c
> @@ -906,6 +906,8 @@ enqueue_task_rt(struct rq *rq, struct ta
>  
>  	if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
>  		enqueue_pushable_task(rq, p);
> +
> +	inc_nr_running(rq);
>  }
>  
>  static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
> @@ -916,6 +918,8 @@ static void dequeue_task_rt(struct rq *r
>  	dequeue_rt_entity(rt_se);
>  
>  	dequeue_pushable_task(rq, p);
> +
> +	dec_nr_running(rq);
>  }
>  
>  /*

I think similar change for sched_stoptask.c is required.

In fact I could not boot tip/master with this v4 patchset.
It reports rcu stall warns without applying following tweak:

--- a/kernel/sched_stoptask.c
+++ b/kernel/sched_stoptask.c
@@ -35,11 +35,13 @@ static struct task_struct *pick_next_task_stop(struct rq *rq
 static void
 enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 {
+       inc_nr_running(rq);
 }

 static void
 dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 {
+       dec_nr_running(rq);
 }


Thanks,
H.Seto

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