Re: [Xen-devel] [PATCH] mem_event: use wait queue when ring is full

[Olaf Hering <olaf@xxxxxxxxx>]

On Fri, Dec 09, Andres Lagar-Cavilla wrote:

> Olaf,
> Tim pointed out we need both solutions to ring management in the
> hypervisor. With our patch ("Improve ring management for memory events. Do
> not lose guest events."), we can handle the common case quickly, without
> preempting VMs. With your patch, we can handle extreme situations of ring
> congestion with the big hammer called wait queue.

With my patch the requests get processed as they come in, both foreign
and target requests get handled equally. There is no special accounting.

A few questions about your requirements:
- Is the goal is that each guest vcpu can always put at least one request?
- How many requests should foreign vcpus place in the ring if the guest
  has more vcpus than available slots in the ring? Just a single one so
  that foreigners can also make some progress?
- Should access and paging have the same rules for accounting?

Olaf

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