[Xen-devel] Xen Hypervisor's memory get roughly less 700MB(even 1400MB) memory than actual grub setting when >4GB

[benian <bestwish.happiness@xxxxxxxxx>]

Hi,

I am using Xen 4.0.1-6 and fedora2.6.32.23-170.xendom0.fc12.x86_64

 

When I try to set the a fix value for memory on grub

 

For example

 

title Xen_Fedora (2.6.32.23-170.xendom0.fc12.x86_64)

        root (hd0,0)

        kernel /xen-4.0.1.gz dom0_mem=5120M

 

I found that when I set dom0_mem<=3GB, the system memory report by “free” “xm list” “xl list” and “xentop” are both approximately conform with the setting in grub.

But when dom_mem>=4GB(roughly), the system memory is obviously different from the grub.

And at the same time, the value reported by “free” and “xm list” , is also obviously different from “xl list” and “xentop”

 

For example, dom0_mem=5120, the reports are:

“free”

                   total       used       free     shared    buffers     cached

Mem:       4489216    1911468    2577748          0       7976     104940

 

“xm list”

Name                 ID   Mem VCPUs      State   Time(s)

Domain-0              0  4384     8     r-----    136.8

 

 

 

“xl list”

Name                 ID   Mem VCPUs       State        Time(s)

Domain-0              0  3648     8        r--    139.8

“xentop”

Mem: 8378584k total, 3850452k used, 4528132k free    CPUs: 8 @ 2660MHz

NAME  STATE   CPU(sec) CPU(%)  MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%) VCPUS

Domain-0 -----r        144    0.9    3735552   44.6   no limit       n/a     8    0       

 

 

Both of them are less 700MB (even 1400 MB) than the setting in grub.

Does anyone have idea about

1.      Why system memory short when dom0_mem >=4GB(roughly)?

2.      why the reported value from “free” and ”xm list “ is different from “xl list” and ”xentop”

 

 

any idea is appreciated .

Thanks very much!

 

Ben

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