Date: Wed, 01 May 2002 23:17:22 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: John Baldwin <jhb@FreeBSD.org> Cc: Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-smp@freebsd.org Subject: Re: hlt when idle? Message-ID: <3CD0D9F2.839890E7@mindspring.com> References: <XFMail.20020501161528.jhb@FreeBSD.org>
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John Baldwin wrote: > > Do both CPUs get clock interrupts on x86? > > No, the interrupts seem to be round-robin, but each clock intr is only > sent to one CPU unlike on alpha where they are broadcast. I was going to make the obvious Alpha comment because it was Andrew asking the question, but since he posted it only to the SMP list and talked about his Pentium III, I didn't. The same is true on SPARC, FWIW. All interrupts on x86 *could* be "broadcast", if the system was run in "virtual wire" mode (MP Spec 1.4). This would *still* break on motherboards that failed to route the clock interrupts via the I/O APIC, though, which is "enough of them to be a large problem". 8-(. Sending an IPI for all processors for the clock interrupt from the processor that receives the clock interrupt is not really a good idea (as I said before), but it's a possible method of achieving "virtual broadcast". As I also said before... "ugly". 8-(. That aside, it might be an OK thing to do on the non-Intel platforms (but again, he was complaining about x86). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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