Messages in this thread | | | Date | Wed, 16 Sep 2009 12:58:42 -0700 | Subject | Re: [PATCH 2/3] ftrace: add tracepoint for xtime | From | john stultz <> |
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On Wed, Sep 16, 2009 at 12:56 PM, john stultz <johnstul@us.ibm.com> wrote: > On Tue, Aug 25, 2009 at 1:14 AM, Zhaolei <zhaolei@cn.fujitsu.com> wrote: >> From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> >> /* Structure holding internal timekeeping values. */ >> struct timekeeper { >> /* Current clocksource used for timekeeping. */ >> @@ -338,6 +341,8 @@ int do_settimeofday(struct timespec *tv) >> >> update_vsyscall(&xtime, timekeeper.clock); >> >> + trace_gtod_update_xtime(&xtime, &wall_to_monotonic); >> + > > So the only thing to watch out on here is that xtime doesn't hold the > current time, but the accumulated time. There is some unaccumulated > time still kept in the clocksource structure. > > You probably want (assuming you only need tick granularity time) to > use current_kernel_time(). > > As an aside, is there a reason you have to have update callbacks and > duplicate the time storage instead of using the existing interfaces? > (ie: Is this due to locking or something else?)
Doh. Sorry, you're actually tracing the timekeeping code. Not using this to assist tracing. Got this confused.
So yea, I think this should be ok, plus or minus determining if you really want xtime or xtime_cache.
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