linux-kernel - Re: [PATCH 3/5] Use next_balance instead of last

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Message-ID: <4540AACE.3010804@yahoo.com.au>
Date:	Thu, 26 Oct 2006 22:32:14 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	unlisted-recipients:; (no To-header on input)
CC:	Christoph Lameter <clameter@....com>, akpm@...l.org,
	Peter Williams <pwil3058@...pond.net.au>,
	linux-kernel@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Dave Chinner <dgc@....com>, Ingo Molnar <mingo@...e.hu>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Subject: Re: [PATCH 3/5] Use next_balance instead of last_balance

Nick Piggin wrote:
> Christoph Lameter wrote:
> 
>> Use next_balance instead of last_balance ...
>>
>> The cpu offset calculation in the sched_domains code makes it 
>> difficult to
>> figure out when the next event is supposed to happen since we only keep
>> track of the last_balancing. We want to know when the next load balance
>> is supposed to occur.
>>
>> Move the cpu offset calculation into build_sched_domains(). Do the
>> setup of the staggered load balance schewduling when the sched domains
>> are initialized. That way we dont have to worry about it anymore later.
>>
>> This also in turn simplifies the load balancing time checks.
> 
> 
> OK. I think I made this overcomplex in order to cope with issues where
> offset can get skewed so if we're unlucky they might all get into synch
> ... but this new code isn't any worse than the old, and it is cheaper.
> 
> So, Ack.

Actually, it is wrong, so nack.

You didn't take into account that balance_interval may have changed,
and so might the idle status.

-- 
SUSE Labs, Novell Inc.
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