Alexander, your one-line patch *does* affect performance on my 64-bit
Linux machine in a worse way than any other proposed patch by calling
sysconf five times. HZ may be defined on your machine, but it isn't on
my (Xeon) machine.

I checked man pages on four different Linuxes (32 bit and 64 bit; SuSE,
Fedora, Ubuntu; recent or six years old). All of them state that using
the sysconf value is the right thing to do. This is also stated in the
man page excerpt in Guido's original bug report.

Neither your latest patch (posixmodule.diff) not my latest patch
(os_times4.PATCH) affects performance; they both only call sysconf once
and then used a cached value.

I'm perfectly fine with your posixmodule.diff, which also meets
Antoine's criteria. I suggest we apply that patch, along with the unit
test from os_times4.PATCH, and be done with it.