[PATCH V2 0/2] nvme: replace linked list with xarray for ns tracking

[Chaitanya Kulkarni]

On 7/1/20 9:50 AM, Sagi Grimberg wrote:
>>>> Hi,
>>>>
>>>> This is a small patch-series which replaces ctrl->namespaces with
>>>> xarray for host-core and target-core. We can see following
>>>> performance improvement when running fio with 32 parallel jobs where
>>>> first 16 namespaces and last 16 namespaces are used for I/O. See [1] for
>>>> detailed performance numbers.
>>> Why would that make any difference given that we don't look up namespaces
>>> in the I/O path?
>> Not in host side. Target does a lookup on each IO through:
>>
>>     nvmet_req_init()
>>       nvmet_parse_io_cmrd()
>>         nvmet_find_namespaces()
>>
>> And this detail should be mentioned in the test setup for the cover
>> letter, or in patch 2.
> Maybe ns scanning performance will improve:)
> 

No it is not about scan only, (although it should as there is no sorting 
involve) this is for the passthru series which uses nvme_find_get_ns() 
in the fast path.