linux-kernel - Re: Disabling physical RAM regions for testing

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Message-ID: <53E0CD59.10003@gmail.com>
Date:	Tue, 05 Aug 2014 08:26:01 -0400
From:	Austin S Hemmelgarn <ahferroin7@...il.com>
To:	madduck@...duck.net
CC:	linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: Disabling physical RAM regions for testing

On 2014-08-05 07:40, martin f krafft wrote:
> Hello,
> 
> A NAS seems to be having RAM problems, leading me to want to swap
> out DIMMs until I found the offender; I'd rather not go to the rack
> every time I need to make a change.
> 
> Is there a way to declare a DIMM unavailable to Linux with a boot
> parameter? There is mem= and memmap= but i cannot figure them out.
> 
> I have two 4Gb DIMMs in there and I just want to disable one, then
> the other…
> 
> This is the e820 physical RAM map:
> 
> [    0.000000] e820: BIOS-provided physical RAM map:
> [    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009e7ff] usable
> [    0.000000] BIOS-e820: [mem 0x000000000009e800-0x000000000009ffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000000e2000-0x00000000000fffff] reserved
> [    0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bff8ffff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000bff9e000-0x00000000bff9ffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000bffa0000-0x00000000bffaa5ff] ACPI data
> [    0.000000] BIOS-e820: [mem 0x00000000bffaa600-0x00000000bffdffff] ACPI NVS
> [    0.000000] BIOS-e820: [mem 0x00000000bffe0000-0x00000000bfffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000e0000000-0x00000000efffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000ffa00000-0x00000000ffffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000022fffffff] usable
> 
> But what do I do with those info?
> 
The e820 is probably not what you want to be looking at.  I would
suggest looking into memory hot-plug/hot-remove support, IIRC the
hot-remove support allows you to bring a bank offline.


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