Improving the kernel/i386 timecounter performance (GSoC proposal)

[Alexander Sack]

On Fri, Mar 27, 2009 at 1:31 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> In message <49CD0405.1060704 at samsco.org>, Scott Long writes:
>
>>I've been talking about this for years.  All I need is help with the VM
>>magic to create the page on fork.  I also want two pages, one global
>>for gettimeofday (and any other global data we can think of) and one
>>per-process for static data like getpid/getgid.
>
> Agreed, that is a good place to start.

I'm assuming folks are still in love with the TSC because it still the
cheapest as oppose ACPI-fast or HPET to even contemplate this?

Also I thought at least PHK's comment (Sergey mentioned it) was true
regardless of bus, that the TSC is not consistent across multiple
packages (and for that matter I suppose cores) due to I *think* its
ISA lineage so how does this work again?  Won't the rate in which you
tick up be sporadic over the course of the process scheduled on
different cores?  (i.e. depending on what core RDTSC happened to land
on)

-aps