Date: Thu, 26 Sep 2013 09:48:44 +0800 From: Julian Elischer <julian@freebsd.org> To: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com> Cc: virtualization@FreeBSD.org Subject: Re: Xen (and others Hypervisors) how do they handle IPIs? Message-ID: <5243927C.9080609@freebsd.org> In-Reply-To: <5242FB81.4090002@citrix.com> References: <5242F9B8.9090300@freebsd.org> <5242FB81.4090002@citrix.com>
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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?
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