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Re: [PATCH 00/05] robust per_cpu allocation for modules

To: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 00/05] robust per_cpu allocation for modules
From: Nick Piggin <nickpiggin@yahoo.com.au>
Date: Sat, 15 Apr 2006 15:32:10 +1000
Cc: LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>, Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>, Andi Kleen <ak@suse.de>, Martin Mares <mj@atrey.karlin.mff.cuni.cz>, bjornw@axis.com, schwidefsky@de.ibm.com, benedict.gaster@superh.com, lethal@linux-sh.org, Chris Zankel <chris@zankel.net>, Marc Gauthier <marc@tensilica.com>, Joe Taylor <joe@tensilica.com>, David Mosberger-Tang <davidm@hpl.hp.com>, rth@twiddle.net, spyro@f2s.com, starvik@axis.com, tony.luck@intel.com, linux-ia64@vger.kernel.org, ralf@linux-mips.org, linux-mips@linux-mips.org, grundler@parisc-linux.org, parisc-linux@parisc-linux.org, linuxppc-dev@ozlabs.org, paulus@samba.org, linux390@de.ibm.com, davem@davemloft.net
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Steven Rostedt wrote:

 would now create a variable called per_cpu_offset__myint in
the .data.percpu_offset section.  This variable will point to the (if
defined in the kernel) __per_cpu_offset[] array.  If this was a module
variable, it would point to the module per_cpu_offset[] array which is
created when the modules is loaded.

If I'm following you correctly, this adds another dependent load
to a per-CPU data access, and from memory that isn't node-affine.

If so, I think people with SMP and NUMA kernels would care more
about performance and scalability than the few k of memory this
saves.

--
SUSE Labs, Novell Inc.
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