linux-kernel - Re: 2.6.25-rc5-git6: Reported regressions from 2.6.24

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Date:	Fri, 21 Mar 2008 22:59:07 +0100
From:	Gabriel C <crazy@...galware.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Gabriel C <nix.or.die@...glemail.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>,
	andi-bz@...stfloor.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: 2.6.25-rc5-git6: Reported regressions from 2.6.24

Thomas Gleixner wrote:
> On Fri, 21 Mar 2008, Gabriel C wrote:
>>>>> Does that make any sense ?
>>>> Not really. Can you please revert the reverted revert again and run
>>>>
>>>> http://people.redhat.com/mingo/time-warp-test/time-warp-test.c
>>>>
>>>> on your machine with all CPUs and HT enabled ?
>>> Sure , doing so now.
>>>
>> Here the result on 2.6.25-rc6-00243-g028011e ( it was running 30++
>> minutes the time I was away for food =) )
>> ...
>>
>>  4 CPUs, running 4 parallel test-tasks.
>> checking for time-warps via:
>> - read time stamp counter (RDTSC) instruction (cycle resolution)
>> - gettimeofday (TOD) syscall (usec resolution)
>> - clock_gettime(CLOCK_MONOTONIC) syscall (nsec resolution)
>>
>> | 1.46 us, TSC-warps:0 | 16.01 us, TOD-warps:0 | 16.10 us, CLOCK-warps:0
> 
> Amazing. I never found a multi socket box where the TSC's were in sync.
> 
> So the rotating watchdog triggers for a yet to figure out reason.
> 
> Oh, now that the pm timer seems to work again, can you try the following:
> 
> apply the reverted patch again and let the box boot. At some point the
> TSC is marked unstable and is replaced by acpi_pm clocksource.
> 
> What result does timewarp.c show in that situation ?

Here it is , same kernel + Andi's patch :

./time-warp-test
4 CPUs, running 4 parallel test-tasks.
checking for time-warps via:
- read time stamp counter (RDTSC) instruction (cycle resolution)
- gettimeofday (TOD) syscall (usec resolution)
- clock_gettime(CLOCK_MONOTONIC) syscall (nsec resolution)

| 1.78 us, TSC-warps:0 | 19.27 us, TOD-warps:0 | 19.37 us, CLOCK-warps:0

> 
> Thanks,
> 	tglx


Gabriel
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