probe hrtimer testing

[Stone, Joshua I]

On Wednesday, May 24, 2006 12:05 PM, William Cohen wrote:
> In the 2.6.17-rc4 kernel it looks like hrtimer is used by
> kernel/itimer.c. Is there a particular benefit explicitly using the
> hrtimer rather than going through the normal timer mechanism? Are
> there other modules that could use the hrtimer directly?

My understanding is that itimers are intended for user-mode processes.
They operate by sending a SIGALRM on expiration, which I don't think we
can use.

The advantage of hrtimers is just the potential for better resolution.
The normal timer mechanism is specified in terms of jiffies.  Currently
hrtimers are also jiffy limited, but since they are specified in
nanoseconds, there's the potential that future arch-specific
implementations will provide accuracy greater than the jiffy rate.

Whether sub-jiffy timers are useful for SystemTap is open for
discussion...


Josh