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Date: Thu, 17 Mar 2011 00:10:01 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Luming Yu <luming.yu@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        John Stultz <johnstul@us.ibm.com>
Subject: Re: what is the better method to do tsc synchronized check?
Message-ID: <20110317041001.GC14675@home.goodmis.org>
References: <AANLkTi=HB7s-VpMAZmNBPgvQadtN9tg91pFY-=atAWsM@mail.gmail.com>
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[ Added Cc's of people that might help you. ]

-- Steve

On Wed, Mar 16, 2011 at 10:56:25PM -0400, Luming Yu wrote:
> Hi there,
> 
> I tested two different methods to do TSC sync check on a Sandy Bridge system.
> The first TSC sync check method is from upstream -38-rc that considers
> TSC is synced.
> The second TSC sync check method is from a 2.6.18 based  kernel that
> considers TSC
> is NOT synced on the Sandy Bridge system. (I modified sync_tsc() to
> just test (not modify TSC) on
> the cpu being tested.)
> 
> [root@intel-sugarbay-DO-01 kernel]# dmesg | grep -i synchroniz
> CPU 1: synchronized TSC with CPU 0 (last diff 29 cycles, maxerr 276 cycles)
> CPU 2: synchronized TSC with CPU 0 (last diff 32 cycles, maxerr 280 cycles)
> CPU 3: synchronized TSC with CPU 0 (last diff 31 cycles, maxerr 284 cycles)
> 
> Do you guy think we need to take 2.6.18-based tsc sync testing method
> rather than the current one in upstream?
> 
> Any inputs are appreciated.
> 
> 
> Thanks
> Luming
> --