From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH 05/10] x86_64: Use generic percpu Date: Sat, 29 Dec 2007 02:55:39 +0100 References: <20071228001046.854702000@sgi.com> <200712281354.52453.ak@suse.de> <47757311.5050503@sgi.com> In-Reply-To: <47757311.5050503@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200712290255.40233.ak@suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Mike Travis Cc: Andrew Morton , Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rusty Russell , tglx@linutronix.de, mingo@redhat.com List-ID: On Friday 28 December 2007 23:05:05 Mike Travis wrote: > Andi Kleen wrote: > > On Friday 28 December 2007 01:10:51 travis@sgi.com wrote: > >> x86_64 provides an optimized way to determine the local per cpu area > >> offset through the pda and determines the base by accessing a remote > >> pda. > > > > And? The rationale for this patch seems to be incomplete. > > > > As far as I can figure out you're replacing an optimized percpu > > implementation which a dumber generic one. Which needs > > at least some description why. > > The specific intent for the next wave of changes coming are to reduce [...] That should be in the changelog of the patch. Anyways the difference between the x86 percpu.h and the generic one is that x86-64 uses a short cut through the PDA to get the current cpu offset for the current CPU case. The generic one goes through smp_processor_id()->array reference instead. I would request that this optimization is not being removed without suitable replacement in the same patchkit. -Andi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org