Messages in this thread | | | Date | Tue, 24 Jun 2008 19:57:53 +0200 | From | Pavel Machek <> | Subject | Re: [RFC PATCH] x86:Use cpu_khz for loops_per_jiffy calculation |
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Hi!
> On X86 platform we can use the value of tsc_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.
How did you adress 'khz has nothing to do with loops per jiffie' comment?
Some cpus can do loop in cycle , some need two cycles, some need half.
Pavel
> @@ -421,6 +422,10 @@ > return; > } > > + lpj = ((u64)tsc_khz * 1000); > + do_div(lpj, HZ); > + lpj_tsc = lpj; > + > printk("Detected %lu.%03lu MHz processor.\n", > (unsigned long)cpu_khz / 1000, > (unsigned long)cpu_khz % 1000); >
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