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RE: [Xen-devel] Regarding TX/RX rings

To: "Mahendra Kutare" <mahendra.kutare@xxxxxxxxx>
Subject: RE: [Xen-devel] Regarding TX/RX rings
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Sat, 23 Oct 2010 23:35:50 +1100
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Thread-topic: [Xen-devel] Regarding TX/RX rings
> The reason I am looking to monitor these rings is to find the variability of
> the data transfer through the TX/RX rings i.e. inbound/outbound network
> traffic. I am doing variability analysis for various combination of VMs
> running in Xen. I am looking at both CPU and Network level metrics. The goal
> is to infer characteristics looking at these lower level metrics about the VMs
> running.
> On my current installation of Xen 3.4.3 with kernel ,  the data
> mentioned in /sys/devices/vbd- or /sys/devices/vif is not available. I need to
> upgrade my kernel.
> I have seen that if I monitor the network traffic input and output throughput
> data (through say xentop running application - RUBiS) it does not really vary
> a lot. So I want to monitor the lower levels to see if there exists
> variability that eventually evens out.

Monitoring just the rings will not tell you about tx-full or rx-starvation 
conditions. You would also need to measure when DomU wants to transmit a packet 
but there is no space left on the tx ring, or when Dom0 has a packet for DomU 
but Dom0 has used all of the rx buffers given by DomU. I would find those 
measurements useful.

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