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From: John <linux.kernel@free.fr>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, tglx@timesys.com, johnstul@us.ibm.com,
	akpm@osdl.org, linux.kernel@free.fr
Subject: Re: One-shot high-resolution POSIX timer periodically late
Date: Wed, 07 Feb 2007 11:13:58 +0100	[thread overview]
Message-ID: <45C9A666.7010703@free.fr> (raw)
In-Reply-To: <20070206123716.GA8481@elte.hu>

Ingo Molnar wrote:

> John wrote:
> 
>> Ingo Molnar wrote:
>> 
>>> 2.6.18-rt7 is pretty old, do you see the problem in 2.6.20-rc6-rt5 too?
>> 
>> Ingo, Thomas,
>> 
>> I cannot reproduce in 2.6.20-rc6-rt6, but it is not strictly an 
>> apples-to-apples comparison because I get a tsc clocksource in 
>> 2.6.20-rc6-rt6, and an acpi_pm clocksource in 2.6.18.6-rt7.
> 
> That suggests that the TSC was not deemed reliable by the newer kernel, 
> which almost always means it's not realiable. I think the problems you 
> were seeing are consistent with TSC being non-monotonic - so the fix is 
> to not use the TSC - and the newer kernel does this automatically.

Ingo,

Perhaps you've mis-read my message?

*2.6.18.6-rt7* installed an acpi_pm clocksource. When I used a boot 
parameter to force the clocksource to tsc, the high-resolution timer 
infrastructure broke (timers expired several *ms* too late).

On the other hand, *2.6.20-rc6-rt6* and *2.6.20-rt2* both installed a 
tsc clock source, and it works.

Therefore, it is not the newer kernel that ignored the tsc, but the 
older kernel. Thus I don't know what to make of your comment :-)

Regards,

John


  reply	other threads:[~2007-02-07 10:16 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <fa.4zD54Ie6Ozt0P4YqQSicS+XzXGw@ifi.uio.no>
     [not found] ` <fa.G+/T32f2o1M3+YGLca/O8NaAQyY@ifi.uio.no>
     [not found]   ` <fa.6Ua8xjNfLKQEZZgDsoJgPMyww4g@ifi.uio.no>
     [not found]     ` <fa.yQlV+WU0TgrJTVqjopa01tgCnT0@ifi.uio.no>
     [not found]       ` <fa.ucVrLJ1Lh6FjdBHRglsIUc8/evk@ifi.uio.no>
     [not found]         ` <fa.Id9oufyELrVbe5Wb8SRakwC0V50@ifi.uio.no>
2007-02-01 10:18           ` John
2007-02-06 12:37             ` Ingo Molnar
2007-02-07 10:13               ` John [this message]
2007-02-05 16:37           ` John
2007-02-06  7:31             ` Peter Zijlstra
2007-02-07 10:25               ` John
2007-02-08 17:32                 ` Thomas Gleixner
2007-02-09 15:25                   ` John
2007-02-09 16:21                     ` Benedikt Spranger
2007-02-09 16:43                     ` Thomas Gleixner
     [not found] <fa.mtUvfgenNQkCc8835prYbwyiPQs@ifi.uio.no>
     [not found] ` <fa.lwkMc548uRMcUjd9KZ2pC1DMKT4@ifi.uio.no>
     [not found]   ` <fa.dTtI0ctv1nu+tCWiK6jGPnrX69k@ifi.uio.no>
     [not found]     ` <fa.CMU3scpnLxfHVWRFPcmfRl2CjhA@ifi.uio.no>
2007-01-30 17:38       ` John
2007-01-30 20:25         ` Ingo Molnar
     [not found] <fa.NwnlFyMPfa3XG6my3HKGWnCW3x4@ifi.uio.no>
     [not found] ` <fa.Ji4GnAbBF2FR5JbSxvxn2haJZIk@ifi.uio.no>
2007-01-25  9:59   ` John
2007-01-25 22:19     ` john stultz
     [not found]   ` <fa.8TBiwbgs8B881k+3X+IlFjhqpLI@ifi.uio.no>
2007-01-25 12:03     ` John
     [not found] <45B729AF.4030701@privacy.net>
2007-01-24 19:02 ` john stultz
2007-01-24 20:09   ` Ingo Molnar

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