Date: Fri, 13 Oct 2006 11:49:04 -0700 From: Chuck Swiger <cswiger@mac.com> To: Eric Hodel <drbrain@segment7.net> Cc: freebsd-performance@FreeBSD.ORG, Kris Kennaway <kris@obsecurity.org> Subject: Re: Help with improving mysql performance on 6.2PRE Message-ID: <9500A2C9-07EB-4EEA-9477-9E6B4BFEB437@mac.com> In-Reply-To: <A2430386-EB9D-4AEE-9144-F7D53D84A9F0@segment7.net> References: <3731.71.56.92.181.1160009571.squirrel@www.stelesys.com> <200610120925.k9C9PmUK048690@lurza.secnetix.de> <20061012205342.GA62241@xor.obsecurity.org> <A2430386-EB9D-4AEE-9144-F7D53D84A9F0@segment7.net>
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On Oct 13, 2006, at 11:26 AM, Eric Hodel wrote: >>> Or did that change recently? >> >> It's only on certain systems, apparently. > > Is there a list of systems where it is safe to use the TSC with > SMP? Or some script we can run? The problem of the TSC clocks getting out of sync affects pretty much all AMD X2 dual-core CPUs, as well as the older 32-bit Althon MP CPUs; the Intel Xeon and Core Duo CPUs seem to do a lot better, although older Intel CPUs have also been reported to show problems with the TSC. Disabling the fancy power-management capabilities (SpeedStep, PowerNow, Cool-n-quiet) to prevent the system from adjusting the CPU clock frequencies seems to reduce the extent of the problem. However, if you want your system clock to work reliably, using the ACPI-safe or i8254 timecounters is going to do much better than using the faster-but-unreliable TSC method. -- -Chuck
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