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Re: Publishing mips_hpt_frequency in /proc/cpuinfo

To: Thomas Gleixner <>
Subject: Re: Publishing mips_hpt_frequency in /proc/cpuinfo
From: Earl Chew <>
Date: Fri, 28 Jan 2011 07:29:10 -0800
Cc: Ralf Baechle <>, "" <>
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Ralf Baechle wrote:
> 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().

Thomas Gleixner wrote:
> Right. We had this discussion on x86 over and over and using a
> vsyscall is the correct approach. That's also a huge win in general if
> you can avoid going into the kernel to read the time. gettimeofday()
> and clock_gettime() belong to the most frequently called syscalls on
> any Linux system.

Ralf, Thomas,

Yes, I have seen that code on x86, and I completely agree with you both. The 
that Ralf described pertinent, but for my currently application the win of
not going to the kernel that Thomas described is much more important.

I would very much like to go down the vsyscall route, but I can't see any
of that infrastructure in the arch/mips subdirectories.

It seems to me that that work has not been started for MIPS.  Am I mistaken ?

[ I'm trying to figure out where I should start. ]

Looking in /proc/cpuinfo for x86 I see:

> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 28
> model name      : Intel(R) Atom(TM) CPU D510   @ 1.66GHz
> stepping        : 10
> cpu MHz         : 1666.670

This makes available the clock frequency of the CPU. To get similar information
for MIPS, I need to rummage around inside dmesg:

> CPU revision is: 00019374 (MIPS 24Kc)
> Atheros AR7161 rev 2, CPU:680.000 MHz, AHB:170.000 MHz, DDR:340.000 MHz

Would you be averse to publishing additional CPU information (include cpu MHz)
in /proc/cpuinfo for MIPS ?


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