[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] x86/x2apic: properly implement cluster mode
On 08/11/2012 15:38, "Jan Beulich" <JBeulich@xxxxxxxx> wrote: >>>> On 08.11.12 at 16:17, Keir Fraser <keir@xxxxxxx> wrote: >> On 08/11/2012 15:03, "Jan Beulich" <JBeulich@xxxxxxxx> wrote: >> >>> So far, cluster mode was just an alternative implementation of >>> physical mode: Allowing only single CPU interrupt targets, and sending >>> IPIs to each target CPU separately. Take advantage of what cluster >>> mode really can do in that regard. >> >> What does it allow? Multicast within certain constraints? > > For IPIs, yes. For interrupts, this gets things merely in line with > cluster mode APIC, specifying more than one destination with > lowest priority delivery. Without actively using the TPR, that > should only affect nested interrupts (which previously would > have got deferred until the outer one finished if their vector > was a lower priority one than the one in service, whereas now > they could get serviced by another CPU within the cluster). > > I also should have pointed out that this has a potential drawback > - it might increase the pressure on vector allocation, since > they're now being shared more heavily (within clusters). But if > someone runs into problems with that, they ought to simply > switch to physical mode (which previously really had no practical > use at all). > >> I know it's not >> part of our coding style, but some comments would be nice. ;) > > Hard to tell what specifically you would want to see commented, > given that this really just extends the originally rather simplistic > implementation. Okay, yes, it doesn't look so complicated re-reading it again. I'm fine with it as it is. -- Keir > Jan > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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