Messages in this thread | | | Date | Tue, 3 Jun 2008 18:20:14 -0700 | From | Arjan van de Ven <> | Subject | Re: [RFC PATCH] x86:Use cpu_khz for loops_per_jiffy calculation |
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On Tue, 03 Jun 2008 17:41:09 -0700 Alok Kataria <akataria@vmware.com> wrote:
> On X86 platform we can use the value of cpu_khz computed during tsc > calibration to calculate the loops_per_jiffy value. Its very > important to keep the error in lpj values to minimum as any error in > that may result in kernel panic in check_timer. > In virtualization environment on a highly overloaded host, the guest > delay calibration may sometimes result in errors beyond the ~50% that > timer_irq_works can handle, resulting in the guest panicking. \
can you guarantee that the rate tsc ticks at is the same as the current CPU frequency? Answer: You can't....
sadly we do need to calibrate this...
In addition, clearly you can have different cpus in a system run at a different rate (both in terms of cpu_khz and, independently, in terms of tsc rate)
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