4GB memory issue with 32bit linux

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4GB memory issue with 32bit linux

Postby kashif » Fri Feb 27, 2009 6:08 pm

aoa,


I am using centos 5.0 32 bit with kernel 2.6.18-53.el5.


I upgraded the memory from 2 GB to 4 GB.

(Currenty I cant use PAE kernel becuase some third party modules have compiled in current kernel )

As per my knowledge 32 bit system support 4GB memory without PAE.

But free command displaying only 3GB.


Code: Select all

  free -m
             total       used       free     shared    buffers     cached
Mem:          3034       2910        123          0         50       2601
-/+ buffers/cache:        258       2775



and dmesg command show this

Code: Select all

 dmesg |grep -i mem
3200MB HIGHMEM available.
896MB LOWMEM available.
Memory for crash kernel (0x0 to 0x0) notwithin permissible range
  HighMem zone: 819200 pages, LIFO batch:31
Memory: 3103732k/4194304k available (2080k kernel code, 40104k reserved, 869k data, 220k init, 2227584k highmem)


and

Code: Select all

 
dmidecode -t 16
# dmidecode 2.7
SMBIOS 2.34 present.

Handle 0x0022, DMI type 16, 15 bytes.
Physical Memory Array
        Location: System Board Or Motherboard
        Use: System Memory
        Error Correction Type: Multi-bit ECC
        Maximum Capacity: 3000000 kB
        Error Information Handle: Not Provided
        Number Of Devices: 12






Can some one explain

3200MB HIGHMEM available.
896MB LOWMEM available.
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Postby lambda » Sat Feb 28, 2009 12:41 am

that's not unusual. linux (and windows -- it's not a linux-only issue) use some of the address space above 3gb for the kernel and hardware drivers. on some systems, you might get as much as 3.5gb.

supposedly there's a way to get linux to use all 4gb (assuming your bios works like that). however, that slows the system down a bit.
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Re:

Postby LinuxFreaK » Mon Mar 02, 2009 9:26 am

Dear kashif,
Salam,

You can solve this issue by using one of these.

1. Use 64 bits OS.
2. Use kernel-hugemem package.
3. Recompile your kernel with huge memory option.

Best Regards.
Farrukh Ahmed
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Postby syedbilalmasaud » Thu Mar 26, 2009 7:23 pm

Dear Kashif ,

I had same problem and it was solved by Installing 64bit OS and hugemem also works for it , if you cannot install 64bit linux


Bilal
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how to check processor 32 bit or 64 bit

Postby khurram48 » Wed Jun 03, 2009 1:31 pm

its better to verify you hardware and OS is it 64 bit or 32 bit

FYI
http://serversguy.blogspot.com/2009/06/ ... 4-bit.html
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Postby lambda » Wed Jun 03, 2009 3:17 pm

it's very unlikely that he can switch to 64bit, if he has to use third-party modules.
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Re: how to check processor 32 bit or 64 bit

Postby Muhammad Saad » Thu Jun 11, 2009 6:47 am

khurram48 wrote:its better to verify you hardware and OS is it 64 bit or 32 bit

FYI
http://serversguy.blogspot.com/2009/06/ ... 4-bit.html


Assalam-o-Alaikum,

I read this post and am curious about what "lm" means; in order to understand why it is specific to 64 bit hardware. Can someone provide a little information?
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Postby lambda » Thu Jun 11, 2009 12:04 pm

like the article says, "long mode".
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