Re: Proper kernel irq time accounting -v3

[Venkatesh Pallipadi]

On Thu, Sep 30, 2010 at 12:59 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> Venkatesh Pallipadi <venki@xxxxxxxxxx> writes:
>>
>> Solution to (1) involves adding extra timing on irq entry/exit to
>> get the fine granularity info and then exporting it to user.
>
> This means RDTSC right?
>
> I am a bit concerned about overhead on systems with high TSC overhead.
> Is there a way to turn this off at runtime for those?
>

Yes. Overhead will be RDTSC.
notsc is a boot option that will disable this. I didn't want to have a
specific run time option to disable this as we would already have
other RDTSC users like native_sched_clock. Do you think we need a
specific option to disable this feature? I don't like adding a runtime
option because it complicates the code a bit (to handle things like
someone turning it off and turning it on later, etc).

Thanks,
Venki
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