Mailinglist Archive: opensuse (686 mails)

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Re: [opensuse] 64 bit vs 32 bit RAM consumption [summary]
В Wed, 24 Jul 2013 13:09:32 -0400
Felix Miata <mrmazda@xxxxxxxxxxxxx> пишет:

On 2013-07-24 12:43 (GMT-0400) Andrey Borzenkov composed:

There is memory range below 4G which is reserved for PCI address
mapping. Size can be quite significant - if you are using 32 bit system
you can lose as much as (or even over) 1G of your memory.

My experience is that reserved space is much closer to negligible:
http://fm.no-ip.com/SS/ram-consumed-server01.png

Top knows nothing about this range. This memory is unavailable
and invisible for operating system.

My notebook has exactly 4GB of physical RAM

bor@opensuse:~> cat /proc/mtrr
reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0c0000000 ( 3072MB), size= 512MB, count=1: write-back
reg03: base=0x100000000 ( 4096MB), size= 512MB, count=1: write-back
reg04: base=0x0dff00000 ( 3583MB), size= 1MB, count=1: uncachable

512MB immediately below 4GB can be made available only by remapping them
above 4GB address space. So you need kernel with support for
addressing of more than 4GB. Which means either 64 bit or PAE.
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