Re: [LSF/MM TOPIC][LSF/MM ATTEND] NAPI polling for block drivers

Stephen Bates
2017-01-12T04:36:51Z

>>
>> I'd like to attend LSF/MM and would like to discuss polling for block
>> drivers.
>>
>> Currently there is blk-iopoll but it is neither as widely used as NAPI
>> in the networking field and accoring to Sagi's findings in [1]
>> performance with polling is not on par with IRQ usage.
>>
>> On LSF/MM I'd like to whether it is desirable to have NAPI like polling
>> in more block drivers and how to overcome the currently seen performance
>> issues.
>
> It would be an interesting topic to discuss, as it is a shame that
> blk-iopoll isn't used more widely.
>
> --
> Jens Axboe
>

I'd also be interested in this topic. Given that iopoll only really makes
sense for low-latency, low queue depth environments (i.e. down below
10-20us) I'd like to discuss which drivers we think will need/want to be
upgraded (aside from NVMe ;-)).

I'd also be interested in discussing how best to enable and disable
polling. In the past some of us have pushed for a "big hammer" to turn
polling on for a given device or HW queue [1]. I'd like to discuss this
again as well as looking at other methods above and beyond the preadv2
system call and the HIPRI flag.

Stephen

[1] http://marc.info/?l=linux-block&m=146307410101827&w=2

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