linux-kernel - Re: PAE problems was [RFC] Reproducible OOM with just a few sleeps

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Message-ID: <510BF3F1.2050605@zytor.com>
Date:	Fri, 01 Feb 2013 08:57:21 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Pavel Machek <pavel@...x.de>
CC:	Phil Turmel <philip@...mel.org>, paul.szabo@...ney.edu.au,
	ben@...adent.org.uk, dave@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: PAE problems was [RFC] Reproducible OOM with just a few sleeps

On 02/01/2013 02:25 AM, Pavel Machek wrote:
>
> On Fri 2013-02-01 11:20:44, Pavel Machek wrote:
>> On Thu 2013-01-31 23:38:27, Phil Turmel wrote:
>>> On 01/31/2013 10:13 PM, paul.szabo@...ney.edu.au wrote:
>>>> [trim /] Does not that prove that PAE is broken?
>>>
>>> Please, Paul, take *yes* for an answer.  It is broken.  You've received
>>> multiple dissertations on why it is going to stay that way.  Unless you
>>> fix it yourself, and everyone seems to be politely wishing you the best
>>> of luck with that.
>>
>> It is not Paul's job to fix PAE. It is job of whoever broke it to do
>> so.
>>
>> If it is broken with 2GB of RAM, it is clearly not the known "lowmem
>> starvation" issue, it is something else... and probably worth
>> debugging.
>>
>> So, Paul, if you have time and interest... Try to find some old kernel
>> version where sleep test works with PAE. Hopefully there is one. Then
>> do bisection... author of the patch should then fix it. (And if not,
>> at least you have patch you can revert.)
>>
>> rjw is worth cc-ing at that point.
>
> Ouch, and... IIRC (hpa should know for sure), PAE is neccessary for
> R^X support on x86, thus getting more common, not less. If it does not
> work, that's bad news.
>
> Actually, if PAE is known broken, it should probably get marked as
> such in Kconfig. That's sure to get some discussion started...
> 									Pavel
>

OK, so by the time this thread gets to me there is of course no 
information in it.

The vast majority of all 32-bit kernels compiled these days are PAE, so 
it would seem rather odd if PAE was totally broken.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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