RE: [Xen-devel] RE:2Gb Memory lost in 2.6.32.36 - 50G memory, maxmem=50G, 2G used for pagetable.

[MaoXiaoyun <tinnycloud@xxxxxxxxxxx>]

 
> Date: Thu, 19 May 2011 10:42:42 -0400
> From: konrad.wilk@xxxxxxxxxx
> To: tinnycloud@xxxxxxxxxxx
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx; jeremy@xxxxxxxx
> Subject: Re: [Xen-devel] RE:2Gb Memory lost in 2.6.32.36 - 50G memory, maxmem=50G, 2G used for pagetable.
>
> > 4) Compare the boot log between kernel 10 and 36, I noticed something different, they have different last_pfn.
> >
> > ===below is 36====
> > Xen: 0000000000000000 - 000000000009a000 (usable)
> > Xen: 000000000009a400 - 0000000000100000 (reserved)
> > Xen: 0000000000100000 - 00000000bf790000 (usable)
> > Xen: 00000000bf790000 - 00000000bf79e000 (ACPI data)
> > Xen: 00000000bf79e000 - 00000000bf7d0000 (ACPI NVS)
> > Xen: 00000000bf7d0000 - 00000000bf7e0000 (reserved)
> > Xen: 00000000bf7ec000 - 00000000c0000000 (reserved)
> > Xen: 00000000e0000000 - 00000000f0000000 (reserved)
> ; > Xen: 00000000fec00000 - 00000000fec01000 (reserved)
> > Xen: 00000000fec8a000 - 00000000fec8b000 (reserved)
> > Xen: 00000000fee00000 - 00000000fee01000 (reserved)
> > Xen: 00000000fff00000 - 0000000100000000 (reserved)
> > Xen: 0000000100000000 - 0000000c6ff09000 (usable)
>
> Ok, C6FF09-100000 is 46GB
>
> > DMI present.
> > AMI BIOS detected: BIOS may corrupt low RAM, working around it.
> > last_pfn = 0xc6ff09 max_arch_pfn = 0x400000000
> > last_pfn = 0xbf790 max_arch_pfn = 0x400000000
> >
> > =========below is 10
> >
> > Xen: 0000000000000000 - 000000000009a400 (usable)
> > Xen: 000000000009a400 - 0000000000100000 (reserved)
> > Xen: 0000000000100000 - 00000000bf790000 (usable)
> > Xen: 00000000bf790000 - 00000000bf79e000 (ACPI data)
> > Xen: 00000000bf79e000 - 00000000bf7d0000 (ACPI NVS)
> > Xe n: 00000000bf7d0000 - 00000000bf7e0000 (reserved)
> > Xen: 00000000bf7ec000 - 00000000c0000000 (reserved)
> > Xen: 00000000e0000000 - 00000000f0000000 (reserved)
> > Xen: 00000000fec00000 - 00000000fec01000 (reserved)
> > Xen: 00000000fec8a000 - 00000000fec8b000 (reserved)
> > Xen: 00000000fee00000 - 00000000fee01000 (reserved)
> > Xen: 00000000fff00000 - 0000000100000000 (reserved)
> > Xen: 0000000100000000 - 000000015fe00000 (usable)
>
> And, 15FE00-100000 = 392704*4K/1K/1K = 1534MB = 1.5G
>
> > DMI present.
> > AMI BIOS detected: BIOS may corrupt low RAM, working around it.
> > last_pfn = 0x15fe00 max_arch_pfn = 0x400000000
> > last_pfn = 0xbf790 max_arch_pfn = 0x400000000
> >
>
> So the problem looks as the .36 is creating a pagetable for the
> memory above the 5G you provided - which sounds correct as
> you gave it 5G a nd the expectation that it can balloon up to 50G.
>
> What happens if you provide dom0_mem=max:5G to clamp on the size?
>
 
Seems nothing different(what is clamp means? ^_^ )
 
released 196361 pages of unused memory
BIOS-provided physical RAM map:
 Xen: 0000000000000000 - 000000000009a000 (usable)
 Xen: 000000000009a400 - 0000000000100000 (reserved)
 Xen: 0000000000100000 - 00000000bf790000 (usable)
 Xen: 00000000bf790000 - 00000000bf79e000 (ACPI data)
 Xen: 00000000bf79e000 - 00000000bf7d0000 (ACPI NVS)
 Xen: 00000000bf7d0000 - 00000000bf7e0000 (reserved)
 Xen: 00000000bf7ec000 - 00000000c0000000 (reserved)
 Xen: 00000000e0000000 - 00000000f0000000 (reserved)
 Xen: 00000000fec00000 - 00000000fec01000 (reserved)
 Xen: 00000000fec8a000 - 00000000fec8b000 (reserved)
 Xen: 00000000fee00000 - 00000000fee01000 (reserved)
 Xen: 00000000fff00000 - 0000000100000000 (reserved)
 Xen: 0000000100000000 - 0000000c6ff09000 (usable)
DMI present.
AMI BIOS detected: BIOS may corrupt low RAM, working around it.
last_pfn = 0xc6ff09 max_arch_pfn = 0x40000 0000
last_pfn = 0xbf790 max_arch_pfn = 0x400000000
init_memory_mapping: 0000000000000000-00000000bf790000
init_memory_mapping: 0000000100000000-0000000c6ff09000
RAMDISK: 019b7000 - 01ec6e00
 
root@xmao # xm info | grep 'memory\|command'
total_memory           : 49143
free_memory            : 45022
node_to_memory         : node0:24424
xen_commandline        : msi=1 iommu=off x2apic=off console=com1,vga com1=115200,8n1 noreboot dom0_mem=max:5G dom0_max_vcpus=4 dom0_vcpus_pin cpuidle=0 cpufreq=none xsave=0
 
root@xmao # free -m
             total       used       free     shared    buffers     cached
Mem:          2360       1136       1224          0         15        122
-/+ buffers/cache:        997       1363
Swap:         1027          0       1027

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