[uml-devel] Re: [uml-user] Network lags

[Jeff Dike <jdike@addtoit.com>]

for_spam@gmx.de said:
> at least, i would be interested in getting to know:
> - why this happens 
> - how to "tune" this, that it doesn`t happen 
> - if this is expected behavour on "heavy loaded systems" or probably a uml
> or host-kernel bug 

As you said, you're making life hard for the host.

My guess as to what's happening is this.

You're generating a ton of IO which is pulling the host's memory into page
cache.  This causes UML to get swapped out because it's not doing anything
except answering a ping once in a while.  When it does have to answer a ping,
it needs to be swapped back in, which might be hard since you're sucking down
a lot of IO bandwidth.

So, I don't think this says too much about whether anything's wrong with
either the host or UML.

Once thing you might try is do the same IO with O_DIRECT.  That won't pollute
the page cache.

				Jeff



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