Hi, the issue is solved. It is related to the CPU frequency driver acpi-cpufreq vs. intel_pstate and the governor powersave vs. performance.
With kernel 4.9 the default CPU frequency driver for my hardware is intel_pstate. And I had the governor set to "powersave" in /etc/default/cpufrequtils. I do not see big performance differences between "powersave" and "performance" settings with intel_pstate. But with kernel 3.16 the default CPU frequency driver is acpi-cpufreq. With my settings in /etc/default/cpufrequtils it running in "powersave" mode which is giving this dramatic performance collapse. With governor "ondemand" or "performance" kernel 3.16 is as fast as kernel 4.9. Sorry for the confusion. Matthias Am 05.02.2017 um 15:37 schrieb johannes hanika: > hi, > > how much do you trust your numbers? they look very weird to me. such a > speedup sounds more like one is running single threaded :) > > did you run it a couple of times one after the other? to rule out disk > prefetching etc? using the minimum time of three consecutive runs may > be a good indication. do you have any detailed logs where the time > goes (i.e. which dt module)? i mean the detailed outputs of dt, or > maybe a run through the kernel's perf? you sure the dt version is > exactly the same? you didn't recompile? > > cheers, > jo > > On Mon, Feb 6, 2017 at 1:34 AM, Matthias Bodenbinder > <matth...@bodenbinder.de> wrote: >> Hi, >> >> I have upgraded my PC to newest chipset and CPU: Kaby Lake, Z270 with >> i7-7700K. >> >> Out of curiosity I did a kernel benchmark. Comparing darktable performance >> with kernel 3.16.0-4-amd64 and 4.9.0-1-amd64. I use the following command to >> run darktable: >> darktable-cli test.CR2 test.jpg --core -d perf -d opencl >> >> The results are surprising for me. Kernel 4.9 very much outperformance >> kernel 3.16. Here are the results with and without opencl (using a Geforce >> GTX750TI): >> >> kernel 3.16 kernel 4.9 >> with opencl 16 s 9 s >> without opencl 120 s 23 s >> >> Without opencl, that is with pure CPU performance, the difference is a >> factor of 5! >> >> Why is that? What am I missing? I can hardly believe that kernel 4.9 is so >> much faster. >> >> Matthias >> >> PS >> I have also posted this message to debian.user and I know that it is >> probably better placed into a kernel developer list. But may be some DT >> expert knows the answer or can eventually verify my results. >> >> ___________________________________________________________________________ >> darktable developer mailing list >> to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org >> ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org
