From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fg-out-1718.google.com (fg-out-1718.google.com [72.14.220.158]) by ozlabs.org (Postfix) with ESMTP id 8A711B6F05 for ; Wed, 30 Jun 2010 15:49:25 +1000 (EST) Received: by fg-out-1718.google.com with SMTP id 16so13146fgg.3 for ; Tue, 29 Jun 2010 22:49:22 -0700 (PDT) Date: Wed, 30 Jun 2010 08:49:26 +0200 From: Richard Cochran To: Timur Tabi Subject: Re: CONFIG_NO_HZ causing poor console responsiveness Message-ID: <20100630064926.GA3792@riccoc20.at.omicron.at> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Cc: Linuxppc-dev Development List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jun 29, 2010 at 02:54:17PM -0500, Timur Tabi wrote: > I'm adding support for a new e500-based board (the P1022DS), and in > the process I've discovered that enabling CONFIG_NO_HZ (Tickless > System / Dynamic Ticks) causes significant responsiveness problems on > the serial console. When I type on the console, I see delays of up to > a half-second for almost every character. It acts as if there's a > background process eating all the CPU. > > I don't have time to debug this thoroughly at the moment. The problem > occurs in the latest kernel, but it appears not to occur in 2.6.32. > > Has anyone else seen anything like this? Yes, with a P2020RDB and kernel 2.6.35-rc1. Serial console is really slow on an otherwise idle machine. I assumed it was a hardware problem. Richard