Re: [PATCH] pmtmr and PRINTK_TIME timings display

[Steven Rostedt <rostedt@goodmis.org>]

> 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 after testing with this 
> small inline assembly snippet:

Just turn off the PM timer by disabling CONFIG_X86_PM_TIMER, then your
laptop should just use the tsc timer.


>From make menuconfig:

 Prompt: Power Management Timer Support                                  │
  │   Defined at drivers/acpi/Kconfig:307                                   │
  │   Depends on: !X86_VOYAGER && !X86_VISWS && !IA64_HP_SIM && (IA64 || X8 │
  │   Location:                                                             │
  │     -> Power management options (ACPI, APM)                             │
  │       -> ACPI (Advanced Configuration and Power Interface) Support      │
  │         -> ACPI Support (ACPI [=y])           

-- Steve