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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Paul Turner <pjt@google.com>
Cc: linux-kernel@vger.kernel.org, Venki Pallipadi <venki@google.com>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>,
	Mike Galbraith <efault@gmx.de>,
	Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
	Ben Segall <bsegall@google.com>, Ingo Molnar <mingo@elte.hu>,
	Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 01/14] sched: track the runnable average on a per-task entitiy basis
Date: Thu, 16 Feb 2012 00:37:08 +0100	[thread overview]
Message-ID: <1329349028.2293.190.camel@twins> (raw)
In-Reply-To: <20120202013826.20844.8708.stgit@kitami.mtv.corp.google.com>

On Wed, 2012-02-01 at 17:38 -0800, Paul Turner wrote:
> +       /*
> +        * Use 1024us as the unit of measurement since it's a reasonable
> +        * approximation of 1ms and fast to compute.
> +        */
> +       delta >>= 10;

ns -> us ?, text talks about ms, slightly confusing

> +       if (!delta)
> +               return 0;
> +       sa->last_runnable_update = now;
> +
> +       delta_w = sa->runnable_avg_period % 1024;

so delta_w is the chunk of this p we already accounted.

> +       if (delta + delta_w >= 1024) {

if delta pushes us over 1024*1024 ns (~1ms) we roll a window.

> +               /* period roll-over */
> +               decayed = 1;
> +
> +               delta_w = 1024 - delta_w;

The distance we need to reach the next window.

> +               BUG_ON(delta_w > delta); 

somehow reading this code took forever, this suggests clarification,
either through better variable names or more comments. Could also mean
I'm a moron and should get more sleep or so :-)

  reply	other threads:[~2012-02-15 23:37 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-02  1:38 [RFC PATCH 00/14] sched: entity load-tracking re-work Paul Turner
2012-02-02  1:38 ` [RFC PATCH 05/14] sched: account for blocked load waking back up Paul Turner
2012-02-16 15:57   ` Peter Zijlstra
2012-02-17 13:00     ` Paul Turner
2012-02-16 16:02   ` Peter Zijlstra
2012-02-17 11:39     ` Paul Turner
2012-02-02  1:38 ` [RFC PATCH 01/14] sched: track the runnable average on a per-task entitiy basis Paul Turner
2012-02-15 23:37   ` Peter Zijlstra [this message]
2012-02-17 11:43     ` Paul Turner
2012-02-16 13:27   ` Peter Zijlstra
2012-02-17 11:44     ` Paul Turner
2012-02-02  1:38 ` [RFC PATCH 07/14] sched: compute load contribution by a group entity Paul Turner
2012-02-02  1:38 ` [RFC PATCH 06/14] sched: aggregate total task_group load Paul Turner
2012-02-17  4:41   ` Nikunj A Dadhania
2012-02-17 10:52     ` Paul Turner
2012-02-02  1:38 ` [RFC PATCH 03/14] sched: aggregate load contributed by task entities on parenting cfs_rq Paul Turner
2012-02-02  1:38 ` [RFC PATCH 04/14] sched: maintain the load contribution of blocked entities Paul Turner
2012-02-16 12:25   ` Peter Zijlstra
2012-02-17 11:53     ` Paul Turner
2012-02-02  1:38 ` [RFC PATCH 02/14] sched: maintain per-rq runnable averages Paul Turner
2012-02-02  1:38 ` [RFC PATCH 08/14] sched: normalize tg load contributions against runnable time Paul Turner
2012-02-15 23:36   ` Peter Zijlstra
2012-02-17 12:32     ` Paul Turner
2012-02-20 16:10       ` Peter Zijlstra
2012-02-17 12:34     ` Peter Zijlstra
2012-02-15 23:38   ` Peter Zijlstra
2012-02-02  1:38 ` [RFC PATCH 09/14] sched: maintain runnable averages across throttled periods Paul Turner
2012-02-02  1:38 ` [RFC PATCH 12/14] sched: update_cfs_shares at period edge Paul Turner
2012-02-02  1:38 ` [RFC PATCH 13/14] sched: make __update_entity_runnable_avg() fast Paul Turner
2012-02-06 20:48   ` Peter Zijlstra
2012-02-17 12:49     ` Paul Turner
2012-02-02  1:38 ` [RFC PATCH 11/14] sched: refactor update_shares_cpu() -> update_blocked_avgs() Paul Turner
2012-02-02  1:38 ` [RFC PATCH 14/14] sched: implement usage tracking Paul Turner
2012-02-16 13:37   ` Peter Zijlstra
2012-02-17 10:54     ` Paul Turner
2012-02-20 16:11       ` Peter Zijlstra
2012-02-16 16:58   ` Peter Zijlstra
2012-02-17 11:32     ` Paul Turner
2012-02-20 16:30       ` Peter Zijlstra
2012-02-29 10:37   ` sched per task ARM fix Pantelis Antoniou
2012-02-29 10:37   ` [PATCH 1/2] sched: entity load-tracking re-work - Fix for ARM Pantelis Antoniou
2012-02-28 17:45     ` Morten Rasmussen
2012-02-28 17:52       ` Pantelis Antoniou
2012-02-29 10:37   ` [PATCH 2/2] sched: load-tracking compile when cgroup undefined Pantelis Antoniou
2012-03-13 16:57   ` [RFC PATCH 14/14] sched: implement usage tracking Vincent Guittot
2012-03-14 15:01     ` Peter Zijlstra
2012-03-14 15:45       ` Vincent Guittot
2012-03-14 15:47       ` Paul Turner
2012-03-15 10:52         ` Peter Zijlstra
2012-03-14 15:44     ` Paul Turner
2012-02-02  1:38 ` [RFC PATCH 10/14] sched: replace update_shares weight distribution with per-entity computation Paul Turner
2012-02-06 20:02 ` [RFC PATCH 00/14] sched: entity load-tracking re-work Peter Zijlstra
2012-02-17  9:07 ` Nikunj A Dadhania
2012-02-17 10:48   ` Paul Turner
2012-02-20  9:41     ` Nikunj A Dadhania
2012-02-21  2:33       ` Paul Turner
2012-02-20 17:01 ` Peter Zijlstra
2012-03-12 10:39 ` Morten Rasmussen
2012-03-13 16:44   ` Paul E. McKenney
2012-03-13 17:08     ` Anca Emanuel
2012-03-13 17:23       ` Paul E. McKenney
2012-03-14  9:03       ` Amit Kucheria
2012-03-14 19:19         ` Paul E. McKenney
2012-03-13 17:28   ` Peter Zijlstra
2012-03-12 10:57 ` Vincent Guittot
2012-03-14 15:59   ` Paul Turner
2012-03-15  9:59     ` Vincent Guittot
2012-04-25 13:07     ` Vincent Guittot

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