Date: Thu, 24 Jan 2008 13:04:15 -0600 From: Richard Todd <rmtodd@ichotolot.servalan.com> To: freebsd-current@freebsd.org Subject: Re: Weird performance behaviour in 7.0 Message-ID: <x7lk6favv4.fsf@ichotolot.servalan.com> In-Reply-To: <servalan.mailinglist.fbsd-current/18328.45282.562906.708945@celery.zuhause.org> (Bruce Albrecht's message of "Thu, 24 Jan 2008 09:38:10 -0600") References: <18328.45282.562906.708945@celery.zuhause.org>
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Bruce Albrecht <bruce@zuhause.org> writes: > This is my first Q6600 based system, and my first 7.0 system, and my > first AMD-64 system and my first ZFS base system, and I'm seeing > something really strange. Every now and then, processes run really > slowly, like at 1/600th (or worse) than it ought to, but it racks up > the CPU time as though it's running full tilt. > > For example, I have this little test program that just does a tight > loop, and most times, it takes about 3 seconds to complete, but right > now, it's taking about 2000 seconds to complete. Right now, it's > consistently running slow, but sometimes it will run slow, but I can > terminate it and start another one which will run at normal speed. This wouldn't by any chance be an Intel 965-chipset-based motherboard with 4G or more of memory, would it? Because there's an interesting little bug in the BIOS on some of those boards which causes the cache-control registers to incorrectly declare a chunk of main memory as uncacheable. This results in random slowdowns depending on whether your process lands in the "bad" zone of memory or not. See http://article.gmane.org/gmane.os.freebsd.stable/50135/ for more details.
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