From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 1/8] block: limit default readahead size for small devices Date: Mon, 21 Nov 2011 19:24:09 +0800 Message-ID: <20111121112409.GA8895@localhost> References: <20111121091819.394895091@intel.com> <20111121093846.121502745@intel.com> <20111121100004.GB5084@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , Linux Memory Management List , "linux-fsdevel@vger.kernel.org" , "Li, Shaohua" , Clemens Ladisch , Jens Axboe , Rik van Riel , LKML , Andi Kleen To: Christoph Hellwig Return-path: Content-Disposition: inline In-Reply-To: <20111121100004.GB5084@infradead.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Nov 21, 2011 at 06:00:04PM +0800, Christoph Hellwig wrote: > On Mon, Nov 21, 2011 at 05:18:20PM +0800, Wu Fengguang wrote: > > This looks reasonable: smaller device tend to be slower (USB sticks as > > well as micro/mobile/old hard disks). > > > > Given that the non-rotational attribute is not always reported, we can > > take disk size as a max readahead size hint. This patch uses a formula > > that generates the following concrete limits: > > Given that you mentioned the rotational flag and device size in this > mail, as well as benchmarking with an intel SSD - did you measure > how useful large read ahead sizes still are with highend Flash device > that have extremly high read IOP rates? I don't know -- I don't have access to such highend devices. However the patch changelog has the simple test script. It would be high appreciated if someone can help collect the data :) Thanks, Fengguang -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org