Re: gettimeofday order of magnitude slower with pmtimer, which is default

[Albert Cahalan]

bert hubert writes:

> Not only is the pm timer slow by design, it also needs to be read
> multiple times to work around a bug in certain hardware.
>
> What is new is that this option is now dependent on CONFIG_EMBEDDED.
> Unless you select this option, the PM Timer will always be used.

Good. Fast but horribly buggy is NOT acceptable as a default.
Go ahead and tweak the settings on YOUR system. Run Gentoo.

I wasted a lot of time trying to figure out why my clock ran
about 1.414 (yes, square root of two) times faster than proper.
It turns out that a normal dual-core AMD box has TSCs that run
at randomly varying and fully independant rates. Before I found
a post to linux-kernel by an AMD employee explaining this, my
thought was that I was probably missing clock ticks from the
BIOS going into SMM mode. That was the problem the previous time
I had clock problems. (so I reduced HZ to 100, etc.)

I'm sure lots of people would never figure out why their clock
is running 41.4% faster than normal. They'd live with it, using
a physical clock mounted on the wall, or switch to a different OS.
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