netdev - Re: [PATCH 2/6] pkt_sched: sch_htb: Consider used jiffies in htb

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Date:	Tue, 09 Dec 2008 11:28:44 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Jarek Poplawski <jarkao2@...il.com>
CC:	David Miller <davem@...emloft.net>, Martin Devera <devik@....cz>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 2/6] pkt_sched: sch_htb: Consider used jiffies in	htb_dequeue()

Jarek Poplawski wrote:
> Next event time should consider jiffies used for recounting. Otherwise
> qdisc_watchdog_schedule() triggers hrtimer immediately with the event
> in the past, and may cause very high ksoftirqd cpu usage (if highres
> is on). This patch charges jiffies globally, so we can skip this in
> htb_do_events().
> 
> Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
> ---
>  net/sched/sch_htb.c |   14 ++++++++++++--
>  1 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
> index d6eb4a7..102866d 100644
> --- a/net/sched/sch_htb.c
> +++ b/net/sched/sch_htb.c
> @@ -685,8 +685,11 @@ static psched_time_t htb_do_events(struct htb_sched *q, int level)
>  		if (cl->cmode != HTB_CAN_SEND)
>  			htb_add_to_wait_tree(q, cl, diff);
>  	}
> -	/* too much load - let's continue on next jiffie (including above) */
> -	return q->now + 2 * PSCHED_TICKS_PER_SEC / HZ;
> +	/*
> +	 * Too much load - let's continue on next jiffie.
> +	 * (Used jiffies are charged later.)
> +	 */
> +	return q->now + 1;
>  

This (including the last patch) is really confusing - q->now doesn't
contain HZ values but psched ticks. Could you describe the overall
algorithm you're trying to implement please?

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