linux-kernel - Re: [PATCH 2/2] sched: readjust the load whenever task

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Message-Id: <1216384984.28405.36.camel@twins>
Date:	Fri, 18 Jul 2008 14:43:03 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Gregory Haskins <ghaskins@...ell.com>
Cc:	stable@...r.kernel.org, linux-rt-users@...r.kernel.org,
	rostedt@...dmis.org, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched: readjust the load whenever task_setprio()
	is invoked

On Thu, 2008-07-03 at 15:37 -0600, Gregory Haskins wrote:
> The load may change with the priority, so be sure to recompute its value.
> 
> Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: Ingo Molnar <mingo@...e.hu>

Right, but in this case we'd need to do the dec/inc load game again
because otherwise we'll skew stuff - see the previuos mail on how
dequeue_task() doesn't actually do that.

Also, it looks like current mainline still has this issue.

OTOH - since prio boosting is a temporal feature, not changing the load
isn't too bad, we ought to get back to where we came from pretty
quickly.



> ---
> 
>  kernel/sched.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index b046754..c3f41b9 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4637,6 +4637,7 @@ void task_setprio(struct task_struct *p, int prio)
>  		p->sched_class = &fair_sched_class;
>  
>  	p->prio = prio;
> +	set_load_weight(p);
>  
>  //	trace_special_pid(p->pid, __PRIO(oldprio), PRIO(p));
>  	prev_resched = _need_resched();
> 

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