cvs commit: src/sys/conf options.i386 src/sys/i386/i386 tsc.c src/sys/i386/conf NOTES

[Dag-Erling Smorgrav]

Nate Lawson <nate at root.org> writes:
> Perhaps you could enable this option by default if it had a corresponding
> check for drift that would disable it if things got out of hand.

There wouldn't be much point in that unless the SMP_TSC option also
forced the TSC to be selected at boot time.  On most SMP systems, the
PIIX timecounter is automatically selected by virtue of being
discovered last.

On a related note, the attached patch converts the SMP_TSC option into
a boot-time tunable.  It also enables the TSC on single-CPU systems
running an SMP kernel, since there is no synchronization problem with
a single CPU.

I must have bad benchmark karma, BTW - I can see no reduction of
context switch time or any other significant performance boost when
using the TSC on my dual Celeron system.

DES
-- 
Dag-Erling Smorgrav - des at ofug.org

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