linux-kernel - CONFIG_HIGHMEM4G and 1GB RAM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <e294b46e0704281326w60f9cecfuace3442791f147b3@mail.gmail.com>
Date:	Sat, 28 Apr 2007 21:26:42 +0100
From:	"Bradley Chapman" <kakadu@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: CONFIG_HIGHMEM4G and 1GB RAM

After installing a second 512MB SODIMM into my laptop, I noticed that
my 2.6.18.3 kernel only detected and used 896MB of the resulting 1GB,
and informed me that I needed to enable high memory in order to access
the remaining 127MB.

While doing so, I noticed that the help text stated that enabling high
memory (in my case, CONFIG_HIGHMEM4G) should only be done if the
system the kernel is running on has more than 1GB, but less than 4GB -
it said that systems with 1GB should leave it off, which resulted in
an eighth of the installed memory going missing. A bit more research
found a three year old thread on this list where it was stated that
enabling CONFIG_HIGHMEM4G sometimes slows the system down due to
sometimes undesirable changes to the way the kernel sets up the memory
map.

Basically, all I want to know is whether or not enabling
CONFIG_HIGHMEM4G for a laptop that has exactly 1GB of RAM will result
in any performance degradation.

TIA,

Brad

P.S: Direct replies please - I'm not subscribed to the list.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/