From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DE176C282CC for ; Sat, 9 Feb 2019 03:41:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A342521903 for ; Sat, 9 Feb 2019 03:41:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="tvpcKDdS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726836AbfBIDlW (ORCPT ); Fri, 8 Feb 2019 22:41:22 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:55806 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726522AbfBIDlV (ORCPT ); Fri, 8 Feb 2019 22:41:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=QaE7Zu+8gweRAP8duRl/JZNe/5/26RIXjEsLTjotRlk=; b=tvpcKDdSHodP1uwtNjW6PwDSq iT/72/zCrS6XhPO8YYiSyfYjAPTzVK2K3HjxJ9PsPibqLrac3yErDHEnQ0lPIUShyOzxJvQyZpgzb 8fIwvYGdQwIvysTg+KO/tkId3KxN39VCt0qZid86WjtqKDN3beAycRHtbbWT91tisgzA8KXUxaEMR U37L0Y9zcwv2tcu6BFxtRimkpoHBU/3YFJuNYZTh4fdrKb/0C6k1/9K8Rc2TEvmAKt0HsOUtNHY0T w20q9oCAcoY9Ja1k+ePY7DpgAlk1g0lmhQFabjbnzKeDXBVoowM1eYbEQZgqlVl55jDFXO/cOpGP9 wSiARRvWA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gsJW1-00046C-CA; Sat, 09 Feb 2019 03:41:17 +0000 Date: Fri, 8 Feb 2019 19:41:17 -0800 From: Matthew Wilcox To: Andrew Morton Cc: Waiman Long , Thomas Gleixner , LKML , Alexey Dobriyan , Kees Cook , linux-fsdevel@vger.kernel.org, Davidlohr Bueso , Miklos Szeredi , Daniel Colascione , Dave Chinner , Randy Dunlap , Marc Zyngier Subject: Re: [patch V2 1/2] genriq: Avoid summation loops for /proc/stat Message-ID: <20190209034117.GC21860@bombadil.infradead.org> References: <20190208134802.218483159@linutronix.de> <20190208135020.925487496@linutronix.de> <20190208143255.9dec696b15f03bf00f4c60c2@linux-foundation.org> <20190208152151.ed4cf0c52e5970fc7a7911f1@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190208152151.ed4cf0c52e5970fc7a7911f1@linux-foundation.org> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Feb 08, 2019 at 03:21:51PM -0800, Andrew Morton wrote: > It sounds like it. A 10khz interrupt will overflow in 4 days... If you've got a 10kHz interrupt, you have a bigger problem. Anything happening 10,000 times a second is going to need interrupt mitigation to perform acceptably. More importantly, userspace can (and must) cope with wrapping. This isn't anything new from Thomas' patch. As long as userspace is polling more often than once a day, it's going to see a wrapped value before it wraps again, so it won't miss 4 billion interrupts.