Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752134AbaJEX7h (ORCPT ); Sun, 5 Oct 2014 19:59:37 -0400 Received: from mail-pd0-f171.google.com ([209.85.192.171]:57841 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751809AbaJEX7f (ORCPT ); Sun, 5 Oct 2014 19:59:35 -0400 Message-ID: <1412553572.11091.29.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days From: Eric Dumazet To: Thomas Gleixner Cc: Christoph Lameter , Richard Cochran , linux-kernel@vger.kernel.org Date: Sun, 05 Oct 2014 16:59:32 -0700 In-Reply-To: References: <20141003120345.GA6652@localhost.localdomain> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2014-10-05 at 23:49 +0200, Thomas Gleixner wrote: > Whats so hard about 64bit counters on 32bit machines? Not hard, but not trivial either. > > > expensive to handle in particular because these counters are used in > > performance critical hotpaths. > > The expensive overhead is a single "adcl" instruction. > Assuming a reader do not care of reading garbage yes, while carry is not yet propagated. -- 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/