RE: Timer patches (nsec support + fastcalls for gettod/clock_gettime for all clocks)

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

Christoph Lameter wrote on Friday, July 09, 2004 3:58 PM
> The following patch is the first edition that is complete in that it
> provides all existing functionality (fastcalls) and enhances various
> interfaces:
>
> 1. Restructure timer interpolators to extract common code and provide a
> structure that can be used from assembly language.
> 2. Remove cmpxchg that causes scalability problems (for all clocks
> including ITC now)
>
> 3. Simplify gettimeofday
>
> 4. Provide new fastcall gettimeofday suitable for all types of clock
> (including cyclone and SN2 RTC). More than factor 10 speed gain on
> machines that did not use ITC clock before.
>
> 5. Provide fastcall path for clock_gettime(CLOCK_REALTIME). Also for all
> clock times. More than a factor 20 gain on this one since it returns
> nanoseconds resolution and thereby avoids the multiplications / division
> and the syscall overhead.
>
> 6. nanosecond resolution for CLOCK_REALTIME and CLOCK_MONOTONIC. This
> yield a 40ns resolution on SN2.
>
> Todo:
> - Test with cyclone machines
> - Test with machines that only have ITC based clocks.
>
> Testind and feedback appreciated.

The C portion works pretty well on ITC based clock.  One java benchmark
that uses gettimeofday heavily gained one percentage point.  The assembly
portion of the fsys call need some more work though, mingetty from the
boot init script falls flat upon booting this patch.

- Ken