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3.3. TSC Timer Synchronization on Opteron CPUs
The current generation of AMD64 Opteron processors can be susceptible to a large
gettimeofday skew. This skew occurs when both cpufreq and the Time Stamp Counter (TSC) are in use. Red Hat Enterprise Linux for Real Time provides a method to prevent this skew by forcing all processors to simultaneously change to the same frequency. As a result, the TSC on a single processor never increments at a different rate than the TSC on another processor.
Procedure 3.2. Enabling TSC Timer Synchronization
- Open the
/etc/default/grubfile in your preferred text editor and append the parametersclocksource=tsc powernow-k8.tscsync=1to theGRUB_CMDLINE_LINUXvariable. This forces the use of TSC and enables simultaneous core processor frequency transitions.GRUB_CMDLINE_LINUX="rd.md=0 rd.lvm=0 rd.dm=0 $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :) rd.luks=0 vconsole.keymap=us rhgb quiet clocksource=tsc powernow-k8.tscsync=1"
- You will need to restart your system for the changes to take effect.
Related Manual Pages
For more information, or for further reading, the following man page is related to the information given in this section.
- gettimeofday(2)
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