linux-kernel - RE: Bug 71331 - mlock yields processor to lower priority process

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Date:	Fri, 21 Mar 2014 14:50:34 +0000
From:	<jimmie.davis@...com.com>
To:	<umgwanakikbuti@...il.com>
CC:	<oneukum@...e.de>, <artem_fetishev@...m.com>,
	<peterz@...radead.org>, <kosaki.motohiro@...fujitsu.com>,
	<linux-kernel@...r.kernel.org>
Subject: RE: Bug 71331 - mlock yields processor to lower priority process


________________________________________
From: Mike Galbraith [umgwanakikbuti@...il.com]
Sent: Friday, March 21, 2014 9:41 AM
To: Davis, Bud @ SSG - Link
Cc: oneukum@...e.de; artem_fetishev@...m.com; peterz@...radead.org; kosaki.motohiro@...fujitsu.com; linux-kernel@...r.kernel.org
Subject: RE: Bug 71331 - mlock yields processor to lower priority process

On Fri, 2014-03-21 at 14:01 +0000, jimmie.davis@...com.com wrote:

> If you call mlock () from a SCHED_FIFO task, you expect it to return
> when done.  You don't expect it to block, and your task to be
> pre-empted.

Say some of your pages are sitting in an nfs swapfile orbiting Neptune,
how do they get home, and what should we do meanwhile?

-Mike

Two options.

#1. Return with a status value of EAGAIN.

or 

#2.  Don't return until you can do it.

If SCHED_FIFO is used, and mlock() is called, the intention of the user is very clear.  Run this task until
it is completed or it blocks (and until a bit ago, mlock() did not block).

SCHED_FIFO users don't care about fairness.  They want the system to do what it is told.

regards,
Bud Davis




 
 

 
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