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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

> 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)
>  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 - 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 and the expectation that it can balloon up to 50G.

What happens if you provide dom0_mem=max:5G to clamp on the size?


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