From: Tony Breeds <tony@bakeyournoodle.com>
To: Joel Schopp <jschopp@austin.ibm.com>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] powerpc: update ibm,client-architecture
Date: Tue, 22 Dec 2009 11:18:19 +1100 [thread overview]
Message-ID: <20091222001819.GL30375@ozlabs.org> (raw)
In-Reply-To: <4B2FBCD1.7080306@austin.ibm.com>
On Mon, Dec 21, 2009 at 12:22:09PM -0600, Joel Schopp wrote:
> 4 is the new 2. Since the actual threads per core is unknown at
> this point in boot you have to be conservative and go with the
> maximum number of any processor. See page 4 of these charts:
> http://www.power.org/events/powercon09/taiwan09/IBM_Overview_POWER7.pdf
Sure P7 /can/ be 4-way SMT, but consider the case where you know you have 128
threads so you set NR_CPUS to 128, then you boot with "max cores" of 32, so you
lose half of your threads. I guess that's only a problem when you build your
own kernels, distros are probably setting NR_CPUS high enough to cover all SMT2
systems anyway.
I guess if the patch only set the "max cores" and described why, I'd (FWIW :D)
be more comfortable.
Yours Tony
prev parent reply other threads:[~2009-12-22 0:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-18 21:07 [PATCH] powerpc: update ibm,client-architecture Joel Schopp
2009-12-20 23:59 ` Michael Neuling
2009-12-21 18:15 ` Joel Schopp
2009-12-21 21:12 ` Michael Neuling
2009-12-21 22:14 ` Joel Schopp
2009-12-22 0:33 ` Michael Neuling
2009-12-22 0:58 ` Tony Breeds
2009-12-21 0:44 ` Tony Breeds
2009-12-21 18:22 ` Joel Schopp
2009-12-22 0:18 ` Tony Breeds [this message]
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