andrew at memset
Aug 3, 2012, 3:33 AM
Post #1 of 1
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Shoehorning a domU and "missing" memory (Xen 4.0.1)
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Hi,
I'm seeing an issue with 4.0.1 on Debian 6 regarding "missing" memory.
My set up:
* Xen 4.0.1 on Debian 6.0.5
* dom0-min-mem 512, enable-dom0-ballooning no, dom0_mem=512M (GRUB
config). (I also tried with dom0-min-mem 0)
* Host server has 32GB RAM
# xm list
Name ID Mem VCPUs State
Time(s)
Domain-0 0 501 8 r-----
12.0
# xm info|grep memory
total_memory : 32758
free_memory : 31832
32758 (total) - 31832 ('free_memory') - 512 (dom0) = 414MB unaccounted.
(No domus are running)
I created an HVM domU with 31488 MB RAM (N.B. this is less than 31832
reported by xm info free_memory plus I calculated about ~250MB memory
overhead) and 4 VCPUs but it wouldn't start due to insufficient memory
available. I expected it to fit.
Is there an official calculation for the memory overhead (for
tables/caches etc)?
Can anyone explain why a domu with 31,488MB won't start when 31,832MB is
free? I'm trying to calculate the most amount of RAM a domU can have
(i.e. to occupy an entire server)
Thanks.
--
Andrew Wade
Memset Ltd., registration number 4504980. 25 Frederick Sanger Road,
Guildford, Surrey, GU2 7YD, UK.
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