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[Xen-devel] Re: Fine-grained proxy resource charging

To: John L Griffin <jlg@xxxxxxxxxx>
Subject: [Xen-devel] Re: Fine-grained proxy resource charging
From: Andi Kleen <ak@xxxxxxx>
Date: 22 Aug 2005 15:18:35 +0200
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, rob.gardner@xxxxxx
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John L Griffin <jlg@xxxxxxxxxx> writes:

> 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.

Consider a xenblk request from different domains that gets merged into
a single request by the elevator. Would you charge the time the driver
spends processing that one to the one domain or the other? Or a xenblk
write the is done in the background by the pdflushd daemons? There are
lots of other cases where IO from different processes gets "mixed" like this. 
And in case of Xen you would even need to track IO from the same process.

Not even standard linux attempts finegrained IO resource tracking and
it would be probably quite complicated and require changes all over in
the host kernel. I don't think it's a particularly good idea.


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