NVMe scalability issue

[Azher Mughal]

I ran some tests last year before SC using 8 drives in a SuperMicro
server. Please see attached. OS was CentOS 6.5 I think.

-Azher

On 6/1/2015 4:02 PM, Keith Busch wrote:
> On Mon, 1 Jun 2015, Ming Lin wrote:
>> Hi list,
>>
>> I'm playing with 8 high performance NVMe devices on a 4 sockets server.
>> Each device can get 730K 4k read IOPS.
>>
>> Kernel: 4.1-rc3
>> fio test shows it doesn't scale well with 4 or more devices.
>> I wonder any possible direction to improve it.
>
> There was a demo at SC'14 with a heck of a lot more NVMe drives than
> that,
> and performance scaled quite linearly. Are your devices sharing PCI-e
> lanes?
>
> You could try setting "cpus_allowed" on each job to the CPU's on the
> socket local to the nvme device. That should get a measurable
> improvement,
> and if your irq's are appropriately affinitized.
>
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