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ACPI-fast default timecounter, but HPET 83% faster

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	ACPI-fast default timecounter, but HPET 83% faster by Pieter de Goeje :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message Dear hackers, While fiddling with the sysctl kern.timecounter.hardware, I found out that on my system HPET is significantly faster than ACPI-fast. Using the program below I measured the number of clock_gettime() calls the system can execute per second. I ran the program 10 times for each configuration and here are the results: x ACPI-fast + HPET +-------------------------------------------------------------------------+ \|x +\| \|x +\| \|x ++\| \|x ++\| \|x ++\| \|x ++\| \|A \|A\| +-------------------------------------------------------------------------+ N Min Max Median Avg Stddev x 10 822032 823752 823551 823397.8 509.43254 + 10 1498348 1506862 1502830 1503267.4 2842.9779 Difference at 95.0% confidence 679870 +/- 1918.94 82.5688% +/- 0.233052% (Student's t, pooled s = 2042.31) System details: Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66GHz (3200.02-MHz 686-class CPU), Gigabyte P35-DS3R motherboard running i386 -CURRENT updated today. Unfortunately I only have one system with a HPET timecounter, so I cannot verify these results on another system. If similar results are obtained on other machines, I think the HPET timecounter quality needs to be increased beyond that of ACPI-fast. Regards, Pieter de Goeje ----- 8< ----- clock_gettime.c ----- 8< ------ #include <sys/time.h> #include <stdio.h> #include <time.h> #define COUNT 1000000 int main() { struct timespec ts_start, ts_stop, ts_read; double time; int i; clock_gettime(CLOCK_MONOTONIC, &ts_start); for(i = 0; i < COUNT; i++) { clock_gettime(CLOCK_MONOTONIC, &ts_read); } clock_gettime(CLOCK_MONOTONIC, &ts_stop); time = (ts_stop.tv_sec - ts_start.tv_sec) + (ts_stop.tv_nsec - ts_start.tv_nsec) * 1E-9; printf("%.0f\n", COUNT / time); } _______________________________________________ freebsd-performance@... mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscribe@..."
	Re: ACPI-fast default timecounter, but HPET 83% faster by Garrett Cooper-6 :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Sun, Apr 26, 2009 at 4:50 PM, Pieter de Goeje <pieter@...> wrote: > Dear hackers, > > While fiddling with the sysctl kern.timecounter.hardware, I found out that on > my system HPET is significantly faster than ACPI-fast. Using the program > below I measured the number of clock_gettime() calls the system can execute > per second. I ran the program 10 times for each configuration and here are > the results: > > x ACPI-fast > + HPET > +-------------------------------------------------------------------------+ > \|x +\| > \|x +\| > \|x ++\| > \|x ++\| > \|x ++\| > \|x ++\| > \|A \|A\| > +-------------------------------------------------------------------------+ > N Min Max Median Avg Stddev > x 10 822032 823752 823551 823397.8 509.43254 > + 10 1498348 1506862 1502830 1503267.4 2842.9779 > Difference at 95.0% confidence > 679870 +/- 1918.94 > 82.5688% +/- 0.233052% > (Student's t, pooled s = 2042.31) > > System details: Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66GHz (3200.02-MHz > 686-class CPU), Gigabyte P35-DS3R motherboard running i386 -CURRENT updated > today. > > Unfortunately I only have one system with a HPET timecounter, so I cannot > verify these results on another system. If similar results are obtained on > other machines, I think the HPET timecounter quality needs to be increased > beyond that of ACPI-fast. > > Regards, > > Pieter de Goeje > > ----- 8< ----- clock_gettime.c ----- 8< ------ > #include <sys/time.h> > #include <stdio.h> > #include <time.h> > > #define COUNT 1000000 > > int main() { > struct timespec ts_start, ts_stop, ts_read; > double time; > int i; > > clock_gettime(CLOCK_MONOTONIC, &ts_start); > for(i = 0; i < COUNT; i++) { > clock_gettime(CLOCK_MONOTONIC, &ts_read); > } > clock_gettime(CLOCK_MONOTONIC, &ts_stop); > > time = (ts_stop.tv_sec - ts_start.tv_sec) + (ts_stop.tv_nsec - > ts_start.tv_nsec) * 1E-9; > printf("%.0f\n", COUNT / time); > } I'm seeing similar results. [root@orangebox /usr/home/gcooper]# dmesg \| grep 'Timecounter "' Timecounter "i8254" frequency 1193182 Hz quality 0 Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 Timecounter "HPET" frequency 14318180 Hz quality 900 [root@orangebox /usr/home/gcooper]# ./cgt 1369355 [root@orangebox /usr/home/gcooper]# sysctl kern.timecounter.hardware="ACPI-fast" kern.timecounter.hardware: HPET -> ACPI-fast [root@orangebox /usr/home/gcooper]# ./cgt 772289 Why's the default ACPI-fast? For power-saving functionality or because of the `quality' factor? What is the criteria that determines the `quality' of a clock as what's being reported above (I know what determines the quality of a clock visually from a oscilloscope =])? Thanks, -Garrett _______________________________________________ freebsd-performance@... mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscribe@..."
	Re: ACPI-fast default timecounter, but HPET 83% faster by John Baldwin :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote: > I'm seeing similar results. > > [root@orangebox /usr/home/gcooper]# dmesg \| grep 'Timecounter "' > Timecounter "i8254" frequency 1193182 Hz quality 0 > Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 > Timecounter "HPET" frequency 14318180 Hz quality 900 > [root@orangebox /usr/home/gcooper]# ./cgt > 1369355 > [root@orangebox /usr/home/gcooper]# sysctl > kern.timecounter.hardware="ACPI-fast" > kern.timecounter.hardware: HPET -> ACPI-fast > [root@orangebox /usr/home/gcooper]# ./cgt > 772289 > > Why's the default ACPI-fast? For power-saving functionality or because > of the `quality' factor? What is the criteria that determines the > `quality' of a clock as what's being reported above (I know what > determines the quality of a clock visually from a oscilloscope =])? I suspect that the quality of the HPET driver is lower simply because no one had measured it previously and HPET is newer and less "proven". -- John Baldwin _______________________________________________ freebsd-performance@... mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscribe@..."
	Re: ACPI-fast default timecounter, but HPET 83% faster by Bruce Cran :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Thu, 30 Apr 2009 08:46:41 -0400 John Baldwin <jhb@...> wrote: > On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote: > > Why's the default ACPI-fast? For power-saving functionality or > > because of the `quality' factor? What is the criteria that > > determines the `quality' of a clock as what's being reported above > > (I know what determines the quality of a clock visually from a > > oscilloscope =])? > > I suspect that the quality of the HPET driver is lower simply because > no one had measured it previously and HPET is newer and less "proven". > http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/dev/acpica/acpi_hpet.c shows some of the history behind the decision. Apparently it used to be slower but it was hoped it would get faster as systems supported it better. I guess that's happening now. -- Bruce Cran _______________________________________________ freebsd-performance@... mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscribe@..."
	Re: ACPI-fast default timecounter, but HPET 83% faster by Kris Kennaway-3 :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message John Baldwin wrote: > On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote: >> I'm seeing similar results. >> >> [root@orangebox /usr/home/gcooper]# dmesg \| grep 'Timecounter "' >> Timecounter "i8254" frequency 1193182 Hz quality 0 >> Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 >> Timecounter "HPET" frequency 14318180 Hz quality 900 >> [root@orangebox /usr/home/gcooper]# ./cgt >> 1369355 >> [root@orangebox /usr/home/gcooper]# sysctl >> kern.timecounter.hardware="ACPI-fast" >> kern.timecounter.hardware: HPET -> ACPI-fast >> [root@orangebox /usr/home/gcooper]# ./cgt >> 772289 >> >> Why's the default ACPI-fast? For power-saving functionality or because >> of the `quality' factor? What is the criteria that determines the >> `quality' of a clock as what's being reported above (I know what >> determines the quality of a clock visually from a oscilloscope =])? > > I suspect that the quality of the HPET driver is lower simply because no one > had measured it previously and HPET is newer and less "proven". > From memory, HPET was massively slower on some of the AMD test hardware I was using. There was a thread about it on one of the mailing lists, but I can't find it right now. Kris _______________________________________________ freebsd-performance@... mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscribe@..."