Messages in this thread | | | Date | Fri, 18 Jul 2014 10:05:00 -0700 | Subject | Re: [PATCH-v2] tracing: Fix wraparound problems in "uptime" tracer | From | Tony Luck <> |
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On Thu, Jul 17, 2014 at 7:08 PM, Steven Rostedt <rostedt@goodmis.org> wrote: >> Do we really need to convert to nanoseconds? Couldn't we just return >> jiffies: > > Sure, and we can make it a "counter". That is, the counters don't hide > 1000 counts on output.
Can you explain that a bit more ... how do we mark it as a "counter"?
>> u64 notrace trace_clock_jiffies(void) >> { >> return jiffies_64 - INITIAL_JIFFIES; >> }
Hmm it seems that we make it hard for applications to see what HZ value the kernel is actually using. All user-facing interfaces should convert to USER_HZ (100). So we should say:
u64 notrace trace_clock_jiffies(void) { return jiffies_64_to_clock_t(jiffies_64 - INITIAL_JIFFIES); }
Do we need to change anything in Documentation/trace/ftrace.txt?
Currently it says:
uptime: This uses the jiffies counter and the time stamp is relative to the time since boot up.
-Tony
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