Date: Thu, 13 Nov 2003 12:20:46 +1100 From: Christopher Vance <vance@aurema.com> To: Daniel Ellard <ellard@eecs.harvard.edu> Cc: John Baldwin <jhb@FreeBSD.org> Subject: Re: Confused about HyperThreading and Performance Message-ID: <20031113012046.GB407@aurema.com> In-Reply-To: <XFMail.20031112180758.jhb@FreeBSD.org> References: <20031112103358.S11644@bowser.eecs.harvard.edu> <XFMail.20031112180758.jhb@FreeBSD.org>
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On Wed, Nov 12, 2003 at 06:07:58PM -0500, John Baldwin wrote: >APIC is not on by default for 4.9, it will be for 5.2. 4.9 does have >HTT on by default when you build an SMP kernel though. Did you include >'options HTT' in your 4.8 SMP kernel? If not, you aren't actually >using your second CPU. Also, as someone else mentioned, setting >'machdep.cpu_idle_hlt=1' can be useful on some HTT systems. However, >p4's have a problem with their interrupt routing that can leave the >second CPU halted for a long time if you do that. Just because you have a cpu with HTT doesn't mean you can use it. Your motherboard and BIOS also need to be aware of it, and enable it. -- Christopher Vance
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