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

To: Christoph Lameter <clameter@sgi.com>
Subject: Re: [PATCH 00/05] robust per_cpu allocation for modules
From: Ravikiran G Thirumalai <kiran@scalex86.org>
Date: Mon, 17 Apr 2006 15:02:38 -0700
Cc: Nick Piggin <nickpiggin@yahoo.com.au>, Steven Rostedt <rostedt@goodmis.org>, 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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On Mon, Apr 17, 2006 at 09:55:02AM -0700, Christoph Lameter wrote:
> On Sat, 15 Apr 2006, Nick Piggin wrote:
> 
> > 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.
> 
> I am also concerned about that. Kiran has a patch to avoid allocpercpu
> having to go through one level of indirection that I guess would no 
> longer work with this scheme.

The alloc_percpu reimplementation would work regardless of changes to
static per-cpu areas.  But, any extra indirection as was proposed initially
is bad IMHO. 

>  
> > 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.
> 
> Right.

Me too :)

Kiran

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