Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752291AbaJCJpM (ORCPT ); Fri, 3 Oct 2014 05:45:12 -0400 Received: from resqmta-po-12v.sys.comcast.net ([96.114.154.171]:41347 "EHLO resqmta-po-12v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751282AbaJCJpK (ORCPT ); Fri, 3 Oct 2014 05:45:10 -0400 Date: Fri, 3 Oct 2014 04:45:08 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Thomas Gleixner cc: linux-kernel@vger.kernel.org Subject: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days Message-ID: Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org struct irq_desc still has unsigned int irq_count; A timer interrupt occurs 1000 times per second and there are 86400 seconds in a day. There is a counter for the local timer interrupt that needs to be continually incremented. So the counter will overflow in 2^32 / 1000 / 86400 = 46 days Diagnostic tools will be surprised by the counters suddenly going back to zero. There may be other interrupt sources that also occur quite often. Is this the way its intended or should the counters be expanded to 64 bit? 64 bit would last for our lifetime. -- 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/