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From: "Ozan Çağlayan" <ozan@pardus.org.tr>
To: linux-kernel@vger.kernel.org
Subject: [RFC] A simple way to determine if the kernel needs HIGHMEM64G to be able to use all the installed memory
Date: Sat, 07 Mar 2009 13:04:38 +0200	[thread overview]
Message-ID: <49B254C6.8010507@pardus.org.tr> (raw)

Hi,

When the installed memory size is >= 4GB, kernel drops some messages like

Warning only 4GB of memory will be used
You have to enable HIGHMEM64G.

I checked that the message comes from arch/x86/init_32.c after checking
max_pfn.

I'm quite dumb about the internal structures of the kernel but, wouldn't it
be possible to create a simple read-only sysfs object like kexec_loaded
that will contain "1" when the kernel needs HIGHMEM64G to see all of the memory
and "0" when it doesn't?

I think that it would be a nice facility for distribution kernels to detect
the need for a PAE enabled 32-bit kernel by just reading some /sys/.. entry.

Thanks,

-- 

Ozan Çağlayan
<ozan_at_pardus.org.tr>

             reply	other threads:[~2009-03-07 11:06 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-03-07 11:04 Ozan Çağlayan [this message]
2009-03-07 19:30 ` [RFC] A simple way to determine if the kernel needs HIGHMEM64G to be able to use all the installed memory Alexey Dobriyan
2009-03-07 19:43   ` Ozan Çağlayan
2009-03-08 20:20     ` Andi Kleen
2009-03-09 13:42       ` [PATCH] x86: suggest running a 64bit kernel on LM capable machines with plenty memory Peter Zijlstra
2009-03-09 19:15         ` Andi Kleen
2009-03-10  9:37           ` Peter Zijlstra
2009-03-10 12:50             ` Andi Kleen
2009-03-10 13:21             ` Arjan van de Ven
2009-03-11 12:01               ` Peter Zijlstra
2009-03-11 12:38                 ` Andi Kleen
2009-03-11 11:47             ` Ingo Molnar

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