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Re: [Xen-devel] Patch: implementing least priority interrupt routing
| To: | Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] Patch: implementing least priority interrupt routing |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Tue, 18 Nov 2008 10:18:18 +0000 |
| Cc: | |
| Delivery-date: | Tue, 18 Nov 2008 02:19:16 -0800 |
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| In-reply-to: | <C5484527.1F525%keir.fraser@xxxxxxxxxxxxx> |
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| Thread-topic: | [Xen-devel] Patch: implementing least priority interrupt routing |
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On 18/11/08 10:10, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote: > Where idle means 'not processing an interrupt'. Which ought to be by far the > most common case even for a non-idle CPU. Does this really improve load > balancing all that much? Does BS2000 spend lots of time in IRQ context? > > My fear is that extra complexity here slows down dest_lowprio for all OSes > (and it's used by a lot of OSes) for every ExtInt delivered. That fear is probably unfounded actually, given we scan a vcpu's IRR bitmap on *every* vmentry currently. Still it would be nice to know the motivation behind this patch (beyond 'it's nice to behave like native hardware'). We might still find a cheaper method with similar or better benefit (e.g., check vcpu_runnable() to find idle VCPUs is cheaper and may be more accurate). -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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