From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id DA8A68D0002 for ; Wed, 17 Nov 2010 18:08:55 -0500 (EST) Date: Wed, 17 Nov 2010 15:08:37 -0800 From: Andrew Morton Subject: Re: [PATCH 06/13] writeback: bdi write bandwidth estimation Message-Id: <20101117150837.a18d56c1.akpm@linux-foundation.org> In-Reply-To: <20101117042850.002299964@intel.com> References: <20101117042720.033773013@intel.com> <20101117042850.002299964@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Jan Kara , Li Shaohua , Christoph Hellwig , Dave Chinner , Theodore Ts'o , Chris Mason , Peter Zijlstra , Mel Gorman , Rik van Riel , KOSAKI Motohiro , linux-mm , linux-fsdevel@vger.kernel.org, LKML List-ID: On Wed, 17 Nov 2010 12:27:26 +0800 Wu Fengguang wrote: > + w = min(elapsed / (HZ/100), 128UL); I did try setting HZ=10 many years ago, and the kernel blew up. I do recall hearing of people who set HZ very low, perhaps because their huge machines were seeing performance prolems when the timer tick went off. Probably there's no need to do that any more. But still, we shouldn't hard-wire the (HZ >= 100) assumption if we don't absolutely need to, and I don't think it is absolutely needed here. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org