Re: Help with improving mysql performance on 6.2PRE

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

_______________________________________________
freebsd-performance@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-performance
To unsubscribe, send any mail to "freebsd-performance-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: Help with improving mysql performance on 6.2PRE
    ... 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 ... the Intel Xeon and Core Duo CPUs seem to do a lot better, ... However, if you want your system clock to work reliably, using the ...
    (freebsd-performance)
  • Re: [PATCH 1/2] ftrace: single CPU tracers use CPU clock
    ... to handle cases where the TSC is out of sync between different CPUs. ... clock and the GTOD clock, we might get some inaccuracy in a single CPU ... with the irqsoff tracer that does not care about other CPUS but cares ...
    (Linux-Kernel)
  • 2.6.20.3-rt8 - DMA suffers excessive delay periodically
    ... Now, I know that this is not a hard real-time system, so it's not the delay per se that I find confusing. ... this is even higher priority than the softirq handlers. ... CLOCK: 367.129000 µs ... TSC: 367.082572 µs ...
    (Linux-Kernel)
  • Re: tsc timer related problems/questions
    ... ACPI turned on, doing this may prevent this from happening. ... When that BUG ... Therefore the TSC is not considered a suitable time source on ... which should check TSC synchronity on the CPUs. ...
    (Linux-Kernel)
  • Re: System clock speed too high - 2.6.3 kernel
    ... There are three clock sources in the x86 kernel, ... The PIT has been in the hardware since, well, day one. ... The TSC is a newer thing so is not available on all ... direct indicator of the cpu speed. ...
    (Linux-Kernel)