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Diffstat (limited to 'stapprobes.5.in')
| -rw-r--r-- | stapprobes.5.in | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/stapprobes.5.in b/stapprobes.5.in index 67070928..b40f21ae 100644 --- a/stapprobes.5.in +++ b/stapprobes.5.in @@ -95,16 +95,24 @@ smaller than N. There are no target variables provided in either context. It is possible for such probes to be run concurrently on a multi-processor computer. .PP -Alternatively, intervals may be specified in units of milliseconds. +Alternatively, intervals may be specified in units of time. There are two probe point variants similar to the jiffies timer: .SAMPLE timer.ms(N) timer.ms(N).randomize(M) .ESAMPLE -Here, N and M are specified in milliseconds. The probe intervals will be -rounded up to the nearest jiffies interval for the actual timer. If the -"randomize" component is given, then the random value will be added to the -interval before the conversion to jiffies. +Here, N and M are specified in milliseconds, but the full options for units +are seconds (s/sec), milliseconds (ms/msec), microseconds (us/usec), +nanoseconds (ns/nsec), and hertz (hz). Randomization is not supported for +hertz timers. + +The actual resolution of the timers depends on the target kernel. For +kernels prior to 2.6.17, timers are limited to jiffies resolution, so +intervals are rounded up to the nearest jiffies interval. After 2.6.17, +the implementation uses hrtimers for tighter precision, though the actual +resolution will be arch-dependent. In either case, if the "randomize" +component is given, then the random value will be added to the interval +before any rounding occurs. .PP Profiling timers are also available to provide probes that execute on all CPUs at the rate of the system tick. This probe takes no parameters. |