Messages in this thread | | | Date | Tue, 15 Nov 2005 10:19:17 -0500 | From | Shailabh Nagar <> | Subject | Re: [Patch 1/4] Delay accounting: Initialization |
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Marcelo Tosatti wrote: > On Mon, Nov 14, 2005 at 08:20:17PM -0800, Andrew Morton wrote: > >>Shailabh Nagar <nagar@watson.ibm.com> wrote: >> >>>+ *ts = sched_clock(); >> >>I'm not sure that it's kosher to use sched_clock() for fine-grained >>timestamping like this. Ingo had issues with it last time this happened? > > > If the system boots with use_rtc == 0 you're going to get jiffies based > resolution from sched_clock(). I have a 1GHz Pentium 3 around here which > does that.
Good point, thanks. This reemphasizes the need for better normalization at output time.
> Maybe use do_gettimeofday() for such systems?
Perhaps getnstimeofday() so resolution isn't reduced to msec level unnecessarily. In these patches, userspace takes responsibility for handling wraparound so delivering a reasonably high-resolution delay data from the kernel is preferable.
> > Would be nice to have a sort of per-arch overridable "gettime()" function? >
Provided as part of this patch ?
>><too lazy to read all the code> Do you normalise these numbers in some >>manner before presenting them to userspace? If so, by what means?
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