From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH 06/13] writeback: bdi write bandwidth estimation Date: Wed, 17 Nov 2010 15:38:27 -0800 Message-ID: <20101117153827.e9f169d1.akpm@linux-foundation.org> References: <20101117042720.033773013@intel.com> <20101117042850.002299964@intel.com> <20101117150837.a18d56c1.akpm@linux-foundation.org> <1290036299.2109.1288.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Wu Fengguang , Jan Kara , Li Shaohua , Christoph Hellwig , Dave Chinner , "Theodore Ts'o" , Chris Mason , Mel Gorman , Rik van Riel , KOSAKI Motohiro , linux-mm , linux-fsdevel@vger.kernel.org, LKML To: Peter Zijlstra Return-path: In-Reply-To: <1290036299.2109.1288.camel@laptop> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Thu, 18 Nov 2010 00:24:59 +0100 Peter Zijlstra wrote: > On Wed, 2010-11-17 at 15:08 -0800, Andrew Morton wrote: > > 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. > > People who do cpu bring-up on very slow FPGAs also lower HZ as far as > possible. grep -r "[^a-zA-Z0-9_]HZ[ ]*/[ ]*100[^0-9]" . :-( -- 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