Re: [Xen-devel] [PATCH 0/2] enable event channel wake-up for mem_event interfaces

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 29/09/2011 07:21, "Keir Fraser" <keir.xen@xxxxxxxxx> wrote:

> On 28/09/2011 14:22, "Adin Scannell" <adin@xxxxxxxxxxxxxxx> wrote:
> 
>> Currently the mem_event code requires a domctl to kick the hypervisor
>> and unpause vcpus.  An event channel is used to notify dom0 of
>> requests placed in the ring, and it can similarly be used to notify
>> Xen, so as not to overuse domctls when running many domains with
>> mem_event interfaces (domctls are not a great interface for this sort
>> of thing, because they will all be serialized).
>> 
>> This patch set enables the use of the event channel to signal when a
>> response in placed in a mem_event ring.
> 
> I don't have an opinion on patch 1/2. I'll leave it to someone else, like
> Tim, to comment.
> 
> Patch 2/2 I don't mind the principle, but the implementation is not very
> scalable. I will post a rewritten version to the list. It might be early
> next week before I do so.

I've attached it. Let me know how it works for you.

 -- Keir

> 
>  -- Keir
> 
>> The two patches are as follows:
>> - The first patch tweaks the memevent code to ensure that no events
>> are lost.  Instead of calling get_response once per kick, we may have
>> to pull out multiple events at a time.  This doesn't affect normal
>> operation with the domctls.
>> This patch also ensures that each vCPU can generate a request in each
>> mem_event ring (i.e. put_request will always work), by appropriately
>> pausing vCPUs when after requests are placed.
>> - The second patch breaks the Xen-side event channel handling into a
>> new arch-specific file "events.c", and adds cases for the different
>> Xen-handled event channels.  This formalizes the tiny exception that
>> was in place for just qemu in event_channel.c.
>> 
>> All the domctls are still in place and everything should be backwards
>> compatible.
>> 
>> Cheers,
>> -Adin
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
> 
>

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