[Xen-devel] Quesiton about Dom0 processing packets for DomUs

["Amitayu Das" <amitayudas@xxxxxxxxx>]

Hi,

I had few questions about Dom0 processing network packets on behalf of other domUs.

1. If multiple domUs have pending packets to be processed and Dom0 is
scheduled, then it processeses the packets (that is, puts them in the
descriptor ring and so on). The question is in what order does it
choose which packet to process? That is, does it just goes through the
network  interrupt list (if any) and serves the packets in a FIFO
manner; or  picks a certain domU and puts all packets belonging to
it, in its respective descriptor ring and then proceeds with some other
domU? If latter is the case, how is the order chosen? Is priority given
to any domU?

2. If there are lot of packets to be processed by Dom0 (say, lot of I/O
is going on by different DomUs) and Dom0 can't process them all within
default time-quantam (I don't know what is the value of it under
different scheduling policy), then is it given any extension or is it
preempted?

3. In addition to processing pending packets, if there are packets to
be transmitted to the network (created by different domUs), then how is
determined if sendiong or receiving should be done first? Or are they
intermixed? How is the respective sending/receving order chosen
(similar to question 1)?

It'll be very helpful if someone can respond to these queries.

Thanks in advance,
Amitayu
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