Any Issues Preventng 4.9.1

[Michael South]

Typographical correction to the patches. It's the _8254_ (timer), not
the _8259_ (PIC).

> OK, I've got it done. Instead of using HPET chips (I don't have ready
> access to such a motherboard), I used the TSC register available on
> Pentium-class CPUs. There are some pluses and minuses to that; high
> precision, _if_ the BIOS doesn't alter the clock frequency for thermal
> or power saving reasons.
> 
> Anyway, it's all attached for your perusal.
> 
> Summary of results:
> Six varieties of code tested:
> 
> 1) Unmodified ckinit.c
> 
> 2) Un-modified ckinit.c, configured with
> USE_TICKS_FOR_CPU_USAGE_STATISTICS=1
> 
> 3) Just commented out I/O
> 
> 4) Re-worked ckinit.c, with new switch CLOCK_DRIVER_USE_TSC = 1.
>    It uses the TSC register on Pentium-class processors.
> 
> 5) Re-worked ckinit.c, with new switch CLOCK_DRIVER_USE_8529 = 1.
>    Equivalent to unmodified ckinit.c.
> 
> 6) Re-worked ckinit.c, with neither ..._USE_TSC nor ..._USE_8529
>    defined. Equivalent to (3).
> 
> Test box is a 500 MHz AMD K6-2.
> 
> 
>       Context switches       nSec per switch
>       per tick (1 KHz)
> 
> (1)         153                    6,525
> (2)       1,582                      632
> (3)       1,025                      976
> (4)         939                    1,065
> (5)         153                    6,524
> (6)       1,117                      895
> 

---
Michael South
msouth at msouth.org
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