linux-kernel - Re: AMD X2 unsynced TSC fix?

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Message-ID: <20061028191800.GA20701@hockin.org>
Date:	Sat, 28 Oct 2006 12:18:00 -0700
From:	thockin@...kin.org
To:	Willy Tarreau <w@....eu>
Cc:	Andi Kleen <ak@...e.de>, Lee Revell <rlrevell@...-job.com>,
	Luca Tettamanti <kronos.it@...il.com>,
	linux-kernel@...r.kernel.org, john stultz <johnstul@...ibm.com>
Subject: Re: AMD X2 unsynced TSC fix?

On Sat, Oct 28, 2006 at 09:15:15PM +0200, Willy Tarreau wrote:
> > While gtod is time critical and often appears high on profile lists it is 
> > normally not as time critical as you're claiming it is; especially not
> > time critical enough to warrant such radical action.
> 
> Yes it was, because the small gain of using a dual core with such
> a workload was clearly lost by that change. IIRC, I reached 25000
> sessions/s on dual core with TSC if I didn't care about the clock,
> 20000 without TSC, and 18000 on single core+TSC. But with the sniffer,
> it was even worse : I had 500 kpps in dual-core+TSC, 70kpps without
> TSC and 300 kpps with single-core+TSC. Since I had to buy the same
> machines for both uses, this last argument was enough for me to stick
> to a single core.

Was the problem that they were not synced at poweron or that they would
drift due to power-states?

Did you try running with idle=poll, to avoid ever entering C1 state (hlt)?

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