Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753327AbaJFPQc (ORCPT ); Mon, 6 Oct 2014 11:16:32 -0400 Received: from resqmta-ch2-10v.sys.comcast.net ([69.252.207.42]:56546 "EHLO resqmta-ch2-10v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753278AbaJFPQa (ORCPT ); Mon, 6 Oct 2014 11:16:30 -0400 Date: Mon, 6 Oct 2014 10:16:28 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Thomas Gleixner cc: Richard Cochran , linux-kernel@vger.kernel.org Subject: Re: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days In-Reply-To: Message-ID: References: <20141003120345.GA6652@localhost.localdomain> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 6 Oct 2014, Thomas Gleixner wrote: > So if you want to fix that as well, you really need to think about the > 32 bit case because there is no serialization for the interrupts which > are delivered directly from their own vector. And no, we should not > diverge 32 and 64 bit artificially here simply because the same 50 > days wrap applies to both. Is it a divergence if both 64bit and 32 bit are unsing unsigned long? > > I really start to wonder whether all this is worth the trouble. It has > been this way forever and 1k timer interrupts per second is not really > a new thing either. So we did not change anything which suddenly makes > tools confused. Tools expect the number of interrupt to increase linearly and not jump by 2^32 once in awhile. There are functions in the kernel (/proc/stat) that sum up various interrupt counters and that are types unsigned long. These larger numbers can suddenly jump by 2^32. Its pretty unusual for a 64 bit conter to do that and it requires some head scratching until we figured that one out. -- 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/