cvs commit: src/sys/amd64/amd64 cpu_switch.S machdep.c

[Poul-Henning Kamp]

In message <20051018094402.A29138 at grasshopper.cs.duke.edu>, Andrew Gallatin wri
tes:

>It is a shame we can't find a way to use the TSC as a timecounter on
>SMP systems.  It seems that about 40% of the context switch time is
>spent just waiting for the PIO read of the ACPI-fast or i8254 to
>return.

No, the shame is that the scheduler tries to partition time rather
than cpu cycles because that approximation got goldplated in some
random standard years back.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.