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Re: [Xen-users] dom0 large and in charge or petite?

Scott Classen wrote:

1. Since I only have 8 threads maybe is this too many domUs? Will they
be constantly fighting over CPU cycles?

Just like multi-tasking without virtual machines, if there are more tasks to run than there are cores to run them on then the tasks will be time shared between the available cores. Some people like to pin a single core for the sole use of Dom0 so as to guarantee no contention and thus best response times for Dom0 tasks (which includes shuffling network packets about.

2. Should dom0 be the most minimal installation needed to administer
the domUs? Do the resources allocated to dom0 affect the performance
of the domUs?

It is "traditional" that Dom0 should have the bare minimum of software installed and running. Compromise Dom0 and you also compromise every guest - thus from a security point of view it's best to minimise the attack vector.

However, if you want, then you can run a full graphical desktop in Dom0 and a few guests as well. particularly useful for experimentation as you can run your normal desktop stuff without tying up a machine for Xen.

3. Should I leave only 1 GB RAM for dom0 and give the rest to the domUs?

General advice seems to be to explicitly limit the ram available to Dom0 (via boot string argument). Several memory structures are sized according to the amount of memory at boot time - and so having Dom0 have access to huge amounts of memory which will actually be used by guests means that it sizes it's data structures accordingly and wastes some memory.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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