[Xen-devel] Fine-grained proxy resource charging

[John L Griffin <jlg@xxxxxxxxxx>]

I am looking into how to charge a domain (say, domain "A") for the 
resources consumed by other service domains (say, B) on behalf of A.  For 
example, charging A for the CPU cycles consumed by the network I/O domain 
(B) as it processes packets produced or consumed by A.

The HP folks recently demonstrate a useful first step (see the Usenix 2005 
paper and the xen-devel post "Yet another Xen performance monitoring tool" 
on 2005-08-18): count the number of page swaps between A and B (as well as 
C and B, D and B, etc.) and use that to approximate how much of B's CPU 
usage should be assigned to A (and C, D, etc.)

I'm pursuing more cycle-accurate methods, in anticipation of non-dom0 
service domains that will do variable amounts of proxy processing, 
especially where the resources consumed (CPU, memory, I/O, larger 
primitives) are not correlated with the amount of interdomain traffic 
between A and B.  For example, a lightweight version of Resource 
Containers (Banga, OSDI 1999) or similar concepts.

The eventual goal would be for B itself to calculate and specify to Xen 
the amount of processing it does on behalf of A and other domains. Looking 
ahead, a possible next step is for Xen to expose to B whether or not A has 
already exceeded its periodic resource allocation, so any schedulers 
inside B can make smarter decisions: for example, not processing packets 
for A when A has temporarily exhausted its allocation.

There aren't many technical details yet; my objective here is to 
synchronize with anyone who's also been thinking about this particular 
problem.

-John


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