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

[Andriy Gapon]

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

From: Andriy Gapon <avg at freebsd.org>
To: =?UTF-8?B?IktPSUUgSGlkZXRha2EgKOmvieaxn+iLsemahu+8oOaVsOeQhuaKgOeglCki?=
 <koie at suri.co.jp>
Cc: bug-followup at freebsd.org
Subject: Re: amd64/152405: wrong user time is reported when CPU frequency
 throttled.
Date: Wed, 24 Nov 2010 15:54:19 +0200

 on 24/11/2010 14:33 KOIE Hidetaka (é¯‰æ±Ÿè‹±éš†ï¼ æ•°ç†æŠ€ç ”) said the following:
 >   | Can you try to boot with kern.eventtimer.timer="i8254" in loader.conf?
 > 
 > Boot process hangs up. (I tried 2 times)
 
 Oh, hm, very strange.  Not sure why that happens.
 
 Anyway, it seems that I missed the real cause of this problem and the excellent
 explanation by Bruce.
 
 Your CPU doesn't have invariant TSC and (x86) FreeBSD doesn't handle that
 correctly for some things like e.g. CPU time accounting that you are reporting about.
 
 This is not a problem for modern hardware which almost universally supports
 invariant TSC, but older models are affected.
 
 -- 
 Andriy Gapon