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

  • To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Amitayu Das" <amitayudas@xxxxxxxxx>
  • Date: Wed, 29 Mar 2006 01:22:28 -0500
  • Delivery-date: Wed, 29 Mar 2006 06:23:57 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>


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,
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