Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751100AbVJRGml (ORCPT ); Tue, 18 Oct 2005 02:42:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751441AbVJRGml (ORCPT ); Tue, 18 Oct 2005 02:42:41 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:60591 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1751100AbVJRGmk (ORCPT ); Tue, 18 Oct 2005 02:42:40 -0400 Date: Tue, 18 Oct 2005 08:42:59 +0200 From: Ingo Molnar To: Daniel Walker Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , david singleton , Steven Rostedt , Rui Nuno Capela , Fernando Lopez-Lezcano , Mark Knecht Subject: Re: 2.6.14-rc4-rt7 Message-ID: <20051018064259.GA21236@elte.hu> References: <20051017160536.GA2107@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=disabled SpamAssassin version=3.0.4 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1279 Lines: 34 * Daniel Walker wrote: > I found this latency ~5 minutes after boot up, no load . It looks like > vgacon_scroll() has a memset like operation which can grow. do you have PRINTK_IGNORE_LOGLEVEL enabled? If yes then much of the printk code will run with interrupts disabled - hence non-preemptable. PRINTK_IGNORE_LOGLEVEL is a debugging feature for developers. I have added an extra explanation to the Kconfig, see below. Ingo Index: linux/lib/Kconfig.debug =================================================================== --- linux.orig/lib/Kconfig.debug +++ linux/lib/Kconfig.debug @@ -18,6 +18,11 @@ config PRINTK_IGNORE_LOGLEVEL distributions disable kernel log messages during certain phases of system startup.) + NOTE: this option also makes printk non-preemptible, + which might improve the output of debugging info or + crash info, but it might also cause latencies if your + kernel is printk-ing alot. + Normally you dont need or want this option. config DEBUG_KERNEL - 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/