54b6680090
Add a native implementation for the sched_clock() function which utilizes the processor-internal cycle counter (Control Register 16) as high-resolution time source. With this patch we now get much more fine-grained resolutions in various in-kernel time measurements (e.g. when viewing the function tracing logs), and probably a more accurate scheduling on SMP systems. There are a few specific implementation details in this patch: 1. On a 32bit kernel we emulate the higher 32bits of the required 64-bit resolution of sched_clock() by increasing a per-cpu counter at every wrap-around of the 32bit cycle counter. 2. In a SMP system, the cycle counters of the various CPUs are not syncronized (similiar to the TSC in a x86_64 system). To cope with this we define HAVE_UNSTABLE_SCHED_CLOCK and let the upper layers do the adjustment work. 3. Since we need HAVE_UNSTABLE_SCHED_CLOCK, we need to provide a cmpxchg64() function even on a 32-bit kernel. 4. A 64-bit SMP kernel which is started on a UP system will mark the sched_clock() implementation as "stable", which means that we don't expect any jumps in the returned counter. This is true because we then run only on one CPU. Signed-off-by: Helge Deller <deller@gmx.de> |
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| .. | ||
| configs | ||
| include | ||
| kernel | ||
| lib | ||
| math-emu | ||
| mm | ||
| oprofile | ||
| defpalo.conf | ||
| install.sh | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| nm | ||