[Lustre-discuss] Lustre clients under Xen

[Oleg Drokin]

Hello!

On Dec 2, 2010, at 10:50 AM, Lukas Hejtmanek wrote:

> On Thu, Dec 02, 2010 at 10:18:51AM -0500, Oleg Drokin wrote:
>> It all depends on how Xen does the shrinking. If it blocks kernel code from execution for long periods of time in process,
>> it's the same as if the node is suspended for some time essentially.
>> Even if it would block only certain threads that tare trying to access to be shrunk memory and it happens to be certain lustre threads,
>> that would still spend trouble if the blocking persists for significant amounts of time.
> It could stop all the processes. And it pages out most used memory into swap. 
> But maybe there are some problems resulting from unlocked pages in lustre 
> threads?

Well, I assume XEN plays nice with others and does not just unlcok pages it did not lock because that would upset everybody, not just Lustre.
In case of Lustre I am sure you'll see tons of tripped assertions.
Lustre does not have any important processes running in userspace, but there are some important kernel threads that should not be deprived of
CPU for too long.

Bye,
    Oleg