linux-kernel - Re: Inconsistent load average on tickless kernels

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Message-ID: <1330534998.11248.158.camel@twins>
Date:	Wed, 29 Feb 2012 18:03:18 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Lesław Kopeć <leslaw.kopec@...za-klasa.pl>
Cc:	Aman Gupta <aman@...1.net>, linux-kernel@...r.kernel.org,
	Chase Douglas <chase.douglas@...onical.com>,
	Damien Wyart <damien.wyart@...e.fr>,
	Kyle McMartin <kyle@...hat.com>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Jonathan Nieder <jrnieder@...il.com>
Subject: Re: Inconsistent load average on tickless kernels

On Wed, 2012-02-29 at 17:24 +0100, Peter Zijlstra wrote:
> 
> The only thing I could find is that on nohz we can confuse the per-rq
> sample period, does the below make a difference? 

Uhm, something like so that is.. 

---
 kernel/sched/core.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d7c4322..44f61df 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2380,7 +2380,8 @@ static void calc_load_account_active(struct rq *this_rq)
 	if (delta)
 		atomic_long_add(delta, &calc_load_tasks);
 
-	this_rq->calc_load_update += LOAD_FREQ;
+	while (!time_before(jiffies, this_rq->calc_load_update))
+		this_rq->calc_load_update += LOAD_FREQ;
 }
 
 /*

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