From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Lameter Subject: RE: [PATCH] percpu: add optimized generic percpu accessors Date: Wed, 28 Jan 2009 11:48:27 -0500 (EST) Message-ID: References: <200901271213.18605.rusty@rustcorp.com.au> <497E705B.5000302@kernel.org> <20090127.134747.153565246.davem@davemloft.net> <497F8F02.9000603@hp.com> <57C9024A16AD2D4C97DC78E552063EA35F317617@orsmsx505.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Rick Jones , David Miller , "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" , "linux-ia64@vger.kernel.org" To: "Luck, Tony" Return-path: Received: from smtp3.ultrahosting.com ([74.213.175.254]:46640 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752335AbZA1R5w (ORCPT ); Wed, 28 Jan 2009 12:57:52 -0500 In-Reply-To: <57C9024A16AD2D4C97DC78E552063EA35F317617@orsmsx505.amr.corp.intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 27 Jan 2009, Luck, Tony wrote: > Managing a larger space could be done ... but at the expense of making > the Alt-DTLB miss handler do a memory lookup to find the physical address > of the per-cpu page needed (assuming that we allocate a bunch of random > physical pages for use as per-cpu space rather than a single contiguous > block of physical memory). We cannot resize the area by using a single larger TLB entry? > When do we know the total amount of per-cpu memory needed? > 1) CONFIG time? Would be easiest. > 2) Boot time? We could make the TLB entry size configurable with a kernel parameter > 3) Arbitrary run time? We could reserve a larger virtual space and switch TLB entries as needed? We would need do get larger order pages to do this.