Re: [PATCH 13/13] lightnvm: Inherit mdts from the parent nvme device

Javier González
2019-03-04T14:06:35Z

> On 4 Mar 2019, at 14.04, Igor Konopko <igor.j.konopko@intel.com> wrote:
>
>
>
>> On 04.03.2019 13:22, Hans Holmberg wrote:
>>> On Mon, Mar 4, 2019 at 12:44 PM Javier González <javier@javigon.com> wrote:
>>>
>>>
>>>
>>>> On 4 Mar 2019, at 12.30, Hans Holmberg <hans@owltronix.com> wrote:
>>>>
>>>> On Mon, Mar 4, 2019 at 10:05 AM Javier González <javier@javigon.com> wrote:
>>>>>> On 27 Feb 2019, at 18.14, Igor Konopko <igor.j.konopko@intel.com> wrote:
>>>>>>
>>>>>> Current lightnvm and pblk implementation does not care
>>>>>> about NVMe max data transfer size, which can be smaller
>>>>>> than 64*K=256K. This patch fixes issues related to that.
>>>>
>>>> Could you describe *what* issues you are fixing?
>
> I'm fixing the issue related to controllers which NVMe max data transfer size is lower that 256K (for example 128K, which happens for existing NVMe controllers and NVMe spec compliant). Such a controllers are not able to handle command which contains 64 PPAs, since the the size of DMAed buffer will be above the capabilities of such a controller.
>

OK. Then let’s try to get support for this ASAP. If the rest agree on a feature bit then it should be straightforward. If not, let’s at least add a warning if MDTS < 64 so that people are able to identify where the missing performance went when updating the kernel if they are not using MDTS on their OCSSD implementations.

Javier