Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752651AbeAEUR1 (ORCPT + 1 other); Fri, 5 Jan 2018 15:17:27 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:39378 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751330AbeAEUR0 (ORCPT ); Fri, 5 Jan 2018 15:17:26 -0500 Subject: Re: [GIT PULL 18/25] lightnvm: set target over-provision on create ioctl To: Javier Gonzalez , =?UTF-8?Q?Matias_Bj=c3=b8rling?= Cc: Jens Axboe , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Hans Holmberg (C)" References: <20180105131621.20808-1-m@bjorling.me> <20180105131621.20808-19-m@bjorling.me> <05ea1992-8dae-f961-b2e0-a93727edc2b5@bjorling.me> From: Randy Dunlap Message-ID: <2d6747af-8287-e9e7-60a7-3047811ce45e@infradead.org> Date: Fri, 5 Jan 2018 12:17:23 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 01/05/2018 11:56 AM, Javier Gonzalez wrote: >> On 5 Jan 2018, at 20.53, Matias Bjørling wrote: >> >> On 01/05/2018 08:52 PM, Javier Gonzalez wrote: >>>> On 5 Jan 2018, at 20.33, Randy Dunlap wrote: >>>> >>>> On 01/05/2018 05:16 AM, Matias Bjørling wrote: >>>>> From: Javier González >>>>> >>>>> Allow to set the over-provision percentage on target creation. In case >>>>> that the value is not provided, fall back to the default value set by >>>>> the target. >>>>> >>>>> In pblk, set the default OP to 11% of the total size of the device >>>> >>>>> +#define PBLK_DEFAULT_OP (11) >>>> >>>> Hi, >>>> Just curious -- where does 11 come from? Is it a spec value? >>> 11 stands for 11% over-provisioning for the media to allow garbage >>> collection. Different SSDs have different values based on the targeted >>> workload - 11% is a common default value for standard drives. >>> The spec. does not specify any default values of over-provisioning. >>> Javier. >> >> I think what Randy means is, why is the value not 20% or 7%, which is the traditional over-provisioning on SSDs. > > We decided 11% based on customer input, but 7% and 20% are also good > default values. I'm ok with having any of those as default - anyone > caring about OP will define the value on target creation, which is the > primary objective of this patch. Got it. Thanks. -- ~Randy