On Thu, Jan 27, 2011 at 08:59:55PM -0800, Earl Chew wrote:
> The CPU frequency is known to the Linux kernel. For example:
>
> > CPU revision is: 00019374 (MIPS 24Kc)
> > Atheros AR7161 rev 2, CPU:680.000 MHz, AHB:170.000 MHz, DDR:340.000 MHz
> > ...
> > Calibrating delay loop... 452.19 BogoMIPS (lpj=2260992)
>
> Unfortunately that information is not available from userspace:
>
> > cpu model : MIPS 24Kc V7.4
> > BogoMIPS : 452.19
>
> This makes it difficult to use CPU timers (rdhwr) from user space
> applications.
>
>
> Is there any reason not to publish mips_hpt_frequency in /proc/cpuinfo ?
The CPU clock frequency may change at any time due to clockscaling A
process might be rescheduled to another CPU running at a different clock
rate. A suspended process might miss counter wraparounds.
This right approach is to handle this in a virtual syscall, something like
vsys_clock_gettime().
Ralf
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