amd64/152405: wrong user time is reported when CPU frequency throttled.

[KOIE Hidetaka ( 鯉江英隆＠数理技研 )]

The following reply was made to PR amd64/152405; it has been noted by GNATS.

From: KOIE Hidetaka (=?iso-2022-jp?B?GyRCOHE5PjFRTjQhdz90TX01OzgmGyhC?=)
 <koie at suri.co.jp>
To: avg at freebsd.org
Cc: bug-followup at freebsd.org
Subject: Re: amd64/152405: wrong user time is reported when CPU frequency
 throttled.
Date: Wed, 24 Nov 2010 16:17:16 +0900 (JST)

   Message-Id: <4CECB71A.7040305 at freebsd.org>
   Date:       Wed, 24 Nov 2010 08:56:26 +0200
   From:       Andriy Gapon <avg at freebsd.org>
   Subject:    Re: amd64/152405: wrong user time is reported when CPU f..
 
   | on 24/11/2010 08:54 KOIE Hidetaka ($B8q9>1QN4!w?tM}5;8&(B) said the following:
   | >   Message-Id: <4CEBE965.5050306 at freebsd.org>
   | >   Date:       Tue, 23 Nov 2010 18:18:45 +0200
   | >   From:       Andriy Gapon <avg at freebsd.org>
   | >   Subject:    Re: amd64/152405: wrong user time is reported when CPU f..
   | > 
   | >   | on 23/11/2010 17:15 KOIE Hidetaka ($B8q9>1QN4!w?tM}5;8&(B) said the following:
   | >   | > I send sysctl kern.timecounter and /var/run/dmesg.boot.
   | >   | 
   | >   | Could you please additionally provide output of sysctl dev.cpu and sysctl machdep?
   | > 
   | > output of sysctl dev.cpu machdep is attached.
   | > 
   | >   | Meanwhile, please also try your test-case after having set the following sysctl
   | >   | kern.eventtimer.choice="i8254".
   | > 
   | > sysctl kern.eventtimer.choice="i8254" fails.
   | 
   | Many apologies, this should have been kern.eventtimer.timer="i8254".
   | Could you please try that?
 
 roger.
 
     % sudo sysctl kern.eventtimer.timer="i8254"
     Password:
     kern.eventtimer.timer: LAPIC -> i8254
     % sudo sysctl dev.cpu.0.freq=1800
     dev.cpu.0.freq: 1800 -> 1800
     % time ./loop
     ffffffff
     0.000u 4.773s 0:00.08 5962.5%   0+0k 0+0io 0pf+0w
     % sudo sysctl dev.cpu.0.freq=1000
     dev.cpu.0.freq: 1800 -> 1000
     % time ./loop
     ffffffff
     0.000u 4.773s 0:00.21 2271.4%   0+0k 0+0io 0pf+0w
     % sleep 1
     ("sleep" had returned after sysctl kern.eventtimer.timer="LAPIC" on another terminal)
     %
 
 NOTE: user time is 0, system time is too long, and elapsed time is too short.
 
 And, wall-clock has been slow...
     % ssh my-server date ; env LANG=C date
     Wed Nov 24 16:03:11 JST 2010
     Wed Nov 24 16:01:15 JST 2010
 
 --
 KOIE Hidetaka