linux-kernel - Re: [PATCH 3/6] sched/fair: Change the variable to hold the number of periods to 32bit integer

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Date:	Fri, 29 Apr 2016 02:33:47 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	bsegall@...gle.com
Cc:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, pjt@...gle.com,
	morten.rasmussen@....com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, juri.lelli@....com
Subject: Re: [PATCH 3/6] sched/fair: Change the variable to hold the number
 of periods to 32bit integer

On Thu, Apr 28, 2016 at 10:29:55AM -0700, bsegall@...gle.com wrote:
> Yuyang Du <yuyang.du@...el.com> writes:
> 
> > Now a period is about 1ms, so a 32-bit unsigned integer can approximately
> > hold a maximum of 49 (=2^32/1000/3600/24) days, which means it is big enough
> > and 64-bit is needless.
> >
> If a thread sleeps for 49 days and then wakes up this would be wrong...
> but it also would just result in it not being decayed to zero, and even
> then only if it was in a very small window, so it doesn't seem like a
> huge deal if it happens.
 
Oh, yeah, and we wouldn't know that task is as sleepy as it realy is. :)