From: Arnd Bergmann <arnd@arndb.de>
To: Martin Peschke <mp3@de.ibm.com>
Subject: Re: [RFC] [Patch 7/8] statistics infrastructure - exploitation prerequisite
Date: Wed, 17 May 2006 01:03:08 +0200
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Am Wednesday 17 May 2006 00:36 schrieb Martin Peschke:
> Any other hints on how to replace my sched_clock() calls are welcome.
> (I want to measure elapsed times in units that are understandable to
> users without hardware manuals and calculator, such as milliseconds.)

There are a number of APIs that allow you to get the time:

- do_gettimeofday
  potentially slow, reliable TOD clock, microsecond resolution
- ktime_get_ts
  monotonic clock, nanosecond resolution
- getnstimeofday
  reliable, nanosecond TOD clock
- xtime
  jiffie accurate TOD clock, with fast reads
- xtime + wall_to_monotonic
  jiffie accurate monotonic clock, almost as fast
- get_cycles
  highest supported resolution and accuracy, highly
  HW-specific behaviour, may overflow.

	Arnd <><
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