Re: [Xen-users] Xen 4.1 on Debian Testing - missing memory

Pasi Kärkkäinen
Sat, 13 Aug 2011 23:18:50 -0000

On Wed, Aug 03, 2011 at 03:48:02PM +0100, Alastair Sherringham
wrote:
> Hello,
>
> I have installed Xen 4.1 on a server Tyan based server machine with
> Debain Wheezy (testing) :
>
> Linux 2.6.39-2-amd64
> xen-hypervisor-4.1-amd64
> 4.1.1-1
>

Please paste "xm info" output.

> The server has 8 dual-core AMD opterons and 8 GB RAM. It is a Tyan
> S4881 motherboard and mezzanine board - 4+4 CPU''s.
>
> On standard Linux, I see all 8 GB RAM.
>
> On a plain install of Xen 4.1 (no configuration or guests), I see 5 GB
> RAM. I assume something in the memory placement/map is causing this.
>

It''s probably a bug in the Linux dom0 kernel.
See: http://wiki.xensource.com/xenwiki/Linux_30_bugs

I think it''s the same bug that causes the "dom0_mem=max:XG is
ignored" issue.

-- Pasi

> Is there anything I can do to see all 8 GB in Xen dom0? The BIOS has
> some options for "node memory" interleaving, memory hole etc. but
I am
> not sure what to do.
>
> I attach some log files and information showing the state.
>
> 1) dmesg - normal Linux
> 2) dmesg.xen - dmeg under Xen dom0
> 3) dmesg.xm - xm dmesg output in Xen dom0
>
> And some memory information here. Any help or advice would be welcome.
>
>
> Normal Linux :
>
> # uname -a
> Linux storserv1 2.6.39-2-amd64 #1 SMP Tue Jul 5 02:51:22 UTC 2011
> x86_64 GNU/Linux
>
> # free
>              total       used       free     shared    buffers     cached
> Mem:       8261616     317948    7943668          0      37108     165968
> -/+ buffers/cache:     114872    8146744
> Swap:      7811000          0    7811000
>
> # cat /proc/meminfo
> MemTotal:        8261616 kB
> MemFree:         7943800 kB
> Buffers:           37132 kB
> Cached:           165964 kB
> SwapCached:            0 kB
> Active:           129904 kB
> Inactive:          98524 kB
> Active(anon):      25472 kB
> Inactive(anon):      464 kB
> Active(file):     104432 kB
> Inactive(file):    98060 kB
> Unevictable:           0 kB
> Mlocked:               0 kB
> SwapTotal:       7811000 kB
> SwapFree:        7811000 kB
> Dirty:                44 kB
> Writeback:             0 kB
> AnonPages:         25404 kB
> Mapped:            11376 kB
> Shmem:               588 kB
> Slab:              33972 kB
> SReclaimable:      14104 kB
> SUnreclaim:        19868 kB
> KernelStack:        1624 kB
> PageTables:         3288 kB
> NFS_Unstable:          0 kB
> Bounce:                0 kB
> WritebackTmp:          0 kB
> CommitLimit:    11941808 kB
> Committed_AS:      95920 kB
> VmallocTotal:   34359738367 kB
> VmallocUsed:       62116 kB
> VmallocChunk:   34359666172 kB
> HardwareCorrupted:     0 kB
> AnonHugePages:         0 kB
> HugePages_Total:       0
> HugePages_Free:        0
> HugePages_Rsvd:        0
> HugePages_Surp:        0
> Hugepagesize:       2048 kB
> DirectMap4k:       51776 kB
> DirectMap2M:     8400896 kB
>
>
> # cat /proc/mtrr
> reg00: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
> reg01: base=0x100000000 ( 4096MB), size= 4096MB, count=1: write-back
> reg02: base=0x200000000 ( 8192MB), size= 1024MB, count=1: write-back
> reg03: base=0x240000000 ( 9216MB), size=  512MB, count=1: write-back
> reg04: base=0x080000000 ( 2048MB), size=  512MB, count=1: write-back
> reg05: base=0x0c0000000 ( 3072MB), size=  256MB, count=1: write-combining
>
> //////////////////////////////////////////////////////////////
>
> Under Xen :
>
> # uname -a
> Linux storserv1 2.6.39-2-amd64 #1 SMP Tue Jul 5 02:51:22 UTC 2011
> x86_64 GNU/Linux
>
> # free
>              total       used       free     shared    buffers     cached
> Mem:       5029700     223128    4806572          0       8680      66008
> -/+ buffers/cache:     148440    4881260
> Swap:      7811000          0    7811000
>
>
> # cat /proc/meminfo
> MemTotal:        5029700 kB
> MemFree:         4806456 kB
> Buffers:            8680 kB
> Cached:            65880 kB
> SwapCached:            0 kB
> Active:            69756 kB
> Inactive:          52608 kB
> Active(anon):      47824 kB
> Inactive(anon):      548 kB
> Active(file):      21932 kB
> Inactive(file):    52060 kB
> Unevictable:          52 kB
> Mlocked:              52 kB
> SwapTotal:       7811000 kB
> SwapFree:        7811000 kB
> Dirty:                 0 kB
> Writeback:             0 kB
> AnonPages:         48028 kB
> Mapped:            12148 kB
> Shmem:               564 kB
> Slab:              30432 kB
> SReclaimable:       8464 kB
> SUnreclaim:        21968 kB
> KernelStack:        1752 kB
> PageTables:         3484 kB
> NFS_Unstable:          0 kB
> Bounce:                0 kB
> WritebackTmp:          0 kB
> CommitLimit:    10325848 kB
> Committed_AS:     178724 kB
> VmallocTotal:   34359738367 kB
> VmallocUsed:       76620 kB
> VmallocChunk:   34359654268 kB
> HardwareCorrupted:     0 kB
> AnonHugePages:         0 kB
> HugePages_Total:       0
> HugePages_Free:        0
> HugePages_Rsvd:        0
> HugePages_Surp:        0
> Hugepagesize:       2048 kB
> DirectMap4k:     9697328 kB
> DirectMap2M:           0 kB
>
>
>
> --
> Alastair Sherringham
> http://www.sherringham.net




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