Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933480AbaFQQFN (ORCPT ); Tue, 17 Jun 2014 12:05:13 -0400 Received: from mail-qg0-f52.google.com ([209.85.192.52]:63286 "EHLO mail-qg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933133AbaFQQFL (ORCPT ); Tue, 17 Jun 2014 12:05:11 -0400 Date: Tue, 17 Jun 2014 12:05:08 -0400 From: Tejun Heo To: Christoph Lameter Cc: "Paul E. McKenney" , David Howells , Linus Torvalds , Andrew Morton , Oleg Nesterov , linux-kernel@vger.kernel.org, Rusty Russell Subject: Re: [PATCH RFC] percpu: add data dependency barrier in percpu accessors and operations Message-ID: <20140617160508.GF31819@htj.dyndns.org> References: <20140612135630.GA23606@htj.dyndns.org> <20140612153426.GV4581@linux.vnet.ibm.com> <20140612155227.GB23606@htj.dyndns.org> <20140617144151.GD4669@linux.vnet.ibm.com> <20140617152752.GC31819@htj.dyndns.org> <20140617160040.GE31819@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140617160040.GE31819@htj.dyndns.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 17, 2014 at 12:00:40PM -0400, Tejun Heo wrote: > Hello, Christoph. > > On Tue, Jun 17, 2014 at 10:56:10AM -0500, Christoph Lameter wrote: > > Uhhh no. The percpu stuff and the associated per cpu atomics are to be > > used for stuff that is per cpu specific and runs at the fastest speed > > doable at that level. Introducing implicit barriers is not that good an > > idea. > > Hmmm? Read barriers are noops on all archs except for alpha and Oops, data dependency barriers, not read barrier. > percpu pointer assignments aren't exactly a high frequency operation > and I'm pretty sure we'll end up with a raw variant anyway. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/