linux-kernel - Re: [GIT PULL 18/25] lightnvm: set target over-provision on create ioctl

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Message-ID: <D8E890A0-DBC8-4C0C-9AB9-62D9BB1CC9F2@cnexlabs.com>
Date:   Fri, 5 Jan 2018 19:52:19 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Randy Dunlap <rdunlap@...radead.org>
CC:     Matias Bjørling <m@...rling.me>,
        Jens Axboe <axboe@...com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Hans Holmberg (C)" <hans.holmberg@...xlabs.com>
Subject: Re: [GIT PULL 18/25] lightnvm: set target over-provision on create
 ioctl

> On 5 Jan 2018, at 20.33, Randy Dunlap <rdunlap@...radead.org> wrote:
> 
> On 01/05/2018 05:16 AM, Matias Bjørling wrote:
>> From: Javier González <javier@...xlabs.com>
>> 
>> 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.

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