Messages in this thread | | | From | Nicolai Stange <> | Subject | Re: [RFC v7 00/23] adapt clockevents frequencies to mono clock | Date | Wed, 21 Sep 2016 01:08:36 +0200 |
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Thomas Gleixner <tglx@linutronix.de> writes:
> On Fri, 16 Sep 2016, Nicolai Stange wrote: > >> Goal: avoid programming ced devices too early for large deltas, for >> details, c.f. the description of [21/23]. >> >> [21-23/23] Actually do the frequency adjustments. >> >> Tested on x86_64 and next-20160916. > > Have you ever measured the overhead of the extra work which has to be done > in clockevents_adjust_all_freqs() ?
Not exactly, I had a look at its invocation frequency which seems to decay exponentially with uptime, presumably because the NTP error approaches zero.
However, I've just gathered a function_graph ftrace on my Intel i7-4800MQ (Haswell, 8HTs):
# tracer: function_graph # # TIME CPU DURATION FUNCTION CALLS # | | | | | | | | 85.287027 | 0) 0.899 us | clockevents_adjust_all_freqs(); 85.288026 | 0) 0.759 us | clockevents_adjust_all_freqs(); 85.289026 | 0) 0.735 us | clockevents_adjust_all_freqs(); 85.290026 | 0) 0.671 us | clockevents_adjust_all_freqs(); 149.503656 | 2) 2.477 us | clockevents_adjust_all_freqs(); 149.507660 | 2) 2.308 us | clockevents_adjust_all_freqs(); 149.511658 | 2) 2.651 us | clockevents_adjust_all_freqs(); 149.545660 | 0) 2.268 us | clockevents_adjust_all_freqs(); 149.564211 | 2) 2.321 us | clockevents_adjust_all_freqs(); 214.351899 | 2) 1.520 us | clockevents_adjust_all_freqs(); 214.354935 | 0) 1.053 us | clockevents_adjust_all_freqs(); 279.026205 | 0) 2.289 us | clockevents_adjust_all_freqs(); 279.030195 | 0) 2.190 us | clockevents_adjust_all_freqs(); 279.034196 | 0) 2.381 us | clockevents_adjust_all_freqs(); 279.047492 | 2) 2.390 us | clockevents_adjust_all_freqs(); 344.250356 | 1) 2.727 us | clockevents_adjust_all_freqs(); 408.879538 | 1) 2.235 us | clockevents_adjust_all_freqs(); 473.125730 | 6) 1.513 us | clockevents_adjust_all_freqs(); 473.129731 | 6) 1.650 us | clockevents_adjust_all_freqs(); 538.387891 | 3) 2.305 us | clockevents_adjust_all_freqs(); 538.391890 | 3) 2.300 us | clockevents_adjust_all_freqs(); 668.257162 | 3) 2.691 us | clockevents_adjust_all_freqs(); 668.261162 | 3) 2.306 us | clockevents_adjust_all_freqs(); 733.459261 | 0) 1.066 us | clockevents_adjust_all_freqs(); 733.463261 | 0) 1.233 us | clockevents_adjust_all_freqs(); 733.467263 | 1) 1.382 us | clockevents_adjust_all_freqs(); 863.398561 | 2) 2.218 us | clockevents_adjust_all_freqs(); 863.402552 | 2) 2.792 us | clockevents_adjust_all_freqs(); 1122.210001 | 3) 2.259 us | clockevents_adjust_all_freqs(); 1122.214004 | 3) 2.165 us | clockevents_adjust_all_freqs(); 1381.283287 | 2) 1.944 us | clockevents_adjust_all_freqs(); 1895.664008 | 2) 1.940 us | clockevents_adjust_all_freqs(); 1895.668009 | 2) 2.041 us | clockevents_adjust_all_freqs(); 2930.385388 | 0) 1.067 us | clockevents_adjust_all_freqs(); 2930.386390 | 5) 1.208 us | clockevents_adjust_all_freqs();
Thanks,
Nicolai
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