Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752650AbeAETx6 (ORCPT + 1 other); Fri, 5 Jan 2018 14:53:58 -0500 Received: from mail-lf0-f54.google.com ([209.85.215.54]:38635 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751751AbeAETx4 (ORCPT ); Fri, 5 Jan 2018 14:53:56 -0500 X-Google-Smtp-Source: ACJfBovDfxTAldoQUWiUrrtORQSYJDBN1Nhst9kEzl+PxEzxOM7d+Lx8CrS/QPRgwK+IgNQwje9MMg== Subject: Re: [GIT PULL 18/25] lightnvm: set target over-provision on create ioctl To: Javier Gonzalez , Randy Dunlap 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> From: =?UTF-8?Q?Matias_Bj=c3=b8rling?= Message-ID: <05ea1992-8dae-f961-b2e0-a93727edc2b5@bjorling.me> Date: Fri, 5 Jan 2018 20:53:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed 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 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.