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Date: Thu, 26 Sep 2013 09:48:44 +0800
From: Julian Elischer <julian@freebsd.org>
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To: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
Subject: Re: Xen (and others Hypervisors) how do they handle IPIs?
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On 9/25/13 11:04 PM, Roger Pau Monné wrote:
> On 25/09/13 16:56, Julian Elischer wrote:
>> If CPUs are mapped around, how are IPIs handled? I assume they must be
>> emulated?
>>
>> I've noticed that under Xen (on both Amazon EC2 and a Redhat server)
>> whenever you schedule a thread it always sits on the run queue for 20
>> uSecs before it starts running. It looks to me like it's the IPI taking
>> a long time to be emulated.
> This has been improved on the FreeBSD Xen PVHVM port by using PV IPIs
> instead of the emulated ones, see r255331. It should be faster than the
> previous emulated implementation.
>
I missed that.. thanks!
Do you (or anyone else) know if this can be used on Amazon EC2?
And do you need a specific version/configuration of Xen to be able to 
use it?