Date: Thu, 25 Nov 2010 04:00:19 GMT From: KOIE Hidetaka (=?iso-2022-jp?B?GyRCOHE5PjFRTjQhdz90TX01OzgmGyhC?=) <koie@suri.co.jp> To: freebsd-amd64@FreeBSD.org Subject: Re: amd64/152405: wrong user time is reported when CPU frequency throttled. Message-ID: <201011250400.oAP40JBN064751@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
The following reply was made to PR amd64/152405; it has been noted by GNATS. From: KOIE Hidetaka (=?iso-2022-jp?B?GyRCOHE5PjFRTjQhdz90TX01OzgmGyhC?=) <koie@suri.co.jp> To: avg@freebsd.org Cc: bug-followup@freebsd.org Subject: Re: amd64/152405: wrong user time is reported when CPU frequency throttled. Date: Thu, 25 Nov 2010 12:56:40 +0900 (JST) Message-Id: <4CED1EEC.5010107@freebsd.org> Date: Wed, 24 Nov 2010 16:19:24 +0200 From: Andriy Gapon <avg@freebsd.org> Subject: Re: amd64/152405: wrong user time is reported when CPU f.. | on 24/11/2010 15:54 Andriy Gapon said the following: | > Anyway, it seems that I missed the real cause of this problem and the excellent | > explanation by Bruce. | | Could you please try the following (work-in-progress) patch? | http://people.freebsd.org/~avg/tsc-cpu_ticks.diff on the patched kernel, time command reports correct time! % sysctl kern.eventtimer.timer kern.eventtimer.timer: LAPIC % sudo sysctl dev.cpu.0.freq=1800 Password: dev.cpu.0.freq: 1800 -> 1800 % time ./loop ffffffff 4.835u 0.007s 0:04.99 96.7% 5+2785k 0+0io 0pf+0w % sudo sysctl dev.cpu.0.freq=1000 dev.cpu.0.freq: 1800 -> 1000 % time ./loop ffffffff 8.754u 0.000s 0:09.12 95.9% 5+2777k 0+0io 0pf+0w % Thank you. | | I expect that it should improve accuracy for your testcase, but may penalize | system performance to certain degree. | | As mav@ has said, performance, accuracy, powerstate management - pick any two of | the three. OTOH, I am not sure by how much the performance could be affected. -- KOIE Hidetaka
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201011250400.oAP40JBN064751>