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SubjectRe: [PATCH] pmtmr and PRINTK_TIME timings display
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On Thu, 2005-08-04 at 17:23 +0200, Borislav Petkov wrote:
> I get it. Actually, I wasn't very sure whether this is the right solution
> since my desktop machine uses tsc timer as default while the laptop the
> pmtmr. I also remember that there was a patch a while ago on lkml which
> enabled a modifiable behavior for PRINTK_TIME through a /proc interface and
> kernel boot option but it somehow didn't get accepted. Ok, then, since we
> keep the jiffies solution across arch's, how can I force the kernel to use
> tsc for printk timings so that i can see the deltas between the different
> printk's instead of the jiffies_64 ns value? The Pentium-M Centrino on the
> laptop evidently supports rdtsc as a msr instruction.

The issue is that there are a number of laptops that do not properly
support cpufreq and additionally newer laptop chips halt their TSC's
when they go into C3 mode. This keeps the TSC from working as a proper
timesource on these systems, and causes the need for alternative
timesources like the ACPI PM timer.

thanks
-john


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