From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] percpu: add optimized generic percpu accessors Date: Tue, 27 Jan 2009 13:47:47 -0800 (PST) Message-ID: <20090127.134747.153565246.davem@davemloft.net> References: <200901271213.18605.rusty@rustcorp.com.au> <497E705B.5000302@kernel.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: tj@kernel.org, rusty@rustcorp.com.au, mingo@elte.hu, herbert@gondor.apana.org.au, akpm@linux-foundation.org, hpa@zytor.com, brgerst@gmail.com, ebiederm@xmission.com, travis@sgi.com, linux-kernel@vger.kernel.org, steiner@sgi.com, hugh@veritas.com, netdev@vger.kernel.org, mathieu.desnoyers@polymtl.ca To: cl@linux-foundation.org Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:50540 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754920AbZA0Vru (ORCPT ); Tue, 27 Jan 2009 16:47:50 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: From: Christoph Lameter Date: Tue, 27 Jan 2009 15:08:57 -0500 (EST) > On Tue, 27 Jan 2009, Tejun Heo wrote: > > > > later). That's because they use TLB tricks for a static 64k per-cpu > > > area, but this doesn't scale. That might not be vital: abandoning > > > that trick will mean they can't optimise read_percpu/read_percpu_var > > > etc as much. > > Why wont it scale? this is a separate TLB entry for each processor. The IA64 per-cpu TLB entry only covers 64k which makes use of it for dynamic per-cpu stuff out of the question. That's why it "doesn't scale"