linux-kernel - Re: PATCH: Allow user to force 'tsc' to be treated as stable.

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Date:	Thu, 5 Feb 2009 22:02:39 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	rusty@...tcorp.com.au
Subject: Re: PATCH:  Allow user to force 'tsc' to be treated as stable.


* Ben Greear <greearb@...delatech.com> wrote:

> Ingo Molnar wrote:
>> * Ben Greear <greearb@...delatech.com> wrote:
>>
>>> Allow user to force TSC as stable clock-source.
>>> Works around BIOS issues in the FWA-7304 (Via CN700 chipset)
>>> system, and possibly others.
>>>
>>> This is against 2.6.29-rc3.
>>
>> What 'issues' does that work around, exactly?
>
> Without this, my system comes up with no stable high-res
> clock, and the getnstimeofday seems to return something
> with around 1ms granularity.  I have HZ set to 1000, so
> its probably just using the 'jiffy' clocksource.
> This in turn screws up my patched version of pktgen and
> likely is sub-optimal for other things as well.
>
> It seems the TSC on this system is stable, but I got lost
> trying to understand the watchdog testing code, so I'm
> not certain if it is wrong or not.  With this force in
> place, the system seems stable and ran overnight under
> network load fine.

What does this tool output:

 http://people.redhat.com/mingo/time-warp-test/time-warp-test.c

? (you can run it both the patched or on the unpatched system)

	Ingo
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