From: "H. Peter Anvin" <hpa@zytor.com>
To: "Alex Villacís Lasso" <a_villacis@palosanto.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Use of memmap= to forcibly recover memory in 3GB-4GB range - is this safe?
Date: Tue, 15 Jan 2013 18:28:49 -0800 [thread overview]
Message-ID: <50F61061.4040201@zytor.com> (raw)
In-Reply-To: <50F606A8.2080804@palosanto.com>
On 01/15/2013 05:47 PM, Alex Villacís Lasso wrote:
>
> The system boots, apparently normally, and I can see the additional
> "memory" in all system reports. However, I cannot quite shake the
> feeling that this "memory" might be in fact an illusion, and an attempt
> to use it will wrap around to the bottom of the memory and corrupt
> anything there. Or worse.
>
> Some tests that I have tried:
> 1) I have tried to occupy as much memory as possible, by starting two
> virtual machines, plus one instance of eclipse, a browser, and a
> bittorrent client, while running the graphical desktop. I have seen the
> free memory (as reported by "top") fall to under 200 Mb with no apparent
> instability, so this should prove that the extra memory is real, right?
> 2) I have recompiled the kernel to support the memtest parameter. When
> using it, the extra memory segment appears to be as healthy as other
> areas of memory. However this might only mean that it is wrapping into
> healthy low RAM.
>
> Is my reasoning sane? Is there a way to know, once and for all, whether
> the extra "memory" is real and safe to use or not?
Maybe you can get memtest86+ to test this phantom memory? But yes, it
does sound like a BIOS bug.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2013-01-16 2:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-16 1:47 Use of memmap= to forcibly recover memory in 3GB-4GB range - is this safe? Alex Villacís Lasso
2013-01-16 2:28 ` H. Peter Anvin [this message]
2013-01-16 7:02 ` Yinghai Lu
2013-01-16 2:29 ` Steven Rostedt
2013-01-16 7:11 ` Yinghai Lu
2013-01-17 0:24 ` Alex Villacís Lasso
2013-01-17 0:31 ` Yinghai Lu
2013-01-17 15:03 ` Martin Mokrejs
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