Bug 598290

Summary: dmesg shows "Memory: ... 788380k absent"
Product: Red Hat Enterprise Linux 5 Reporter: Lin Avator <lavator>
Component: kernelAssignee: Red Hat Kernel Manager <kernel-mgr>
Status: CLOSED NOTABUG QA Contact: Red Hat Kernel QE team <kernel-qe>
Severity: medium Docs Contact:
Priority: low    
Version: 5.2   
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 2010-06-04 14:12:51 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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system log files none

Description Lin Avator 2010-06-01 02:45:30 UTC 
Created attachment 418435 [details]
system log files

Description of problem:

   We install RHEL 5.2 x86_64 on our AMD platform, then we update the kernel to 2.6.33 ( http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.33.tar.gz ) . The output of `dmesg` shows the following message. We are curious that where is the absent 788380k memory gone ? And how could we get them back ?

=====
Memory: 16392812k/17563648k available (3061k kernel code, 788380k absent, 382456k reserved, 5034k data, 468k init)
=====

  Although this is not RHEL bug, we hope to get help from the experts here. Some system logs (dmesg, dmidecode, /proc/iomem, /proc/meminfo, vmstat -s) are collected as f01.zip. Please help to resolve this issue.
Comment 1 Prarit Bhargava 2010-06-04 14:12:51 UTC 
Lin, absent memory reflects the memory addressing space lost due to memory holes in the memory map.  Typically holes are left for PCI space, IO, etc..  Every vendor model system is different, and every system will have a different value reported for the absent memory.

Bottom line: It is not physical memory.

Hope this helps,

P.
Comment 2 Lin Avator 2010-06-07 02:43:41 UTC 
Hi Prarit,

  I got it. Thanks for sharing information.

  Sincerely Yours,
Lin