Re: [LSF/MM/BPF TOPIC] Improving Zoned Storage Support

Jens Axboe
2024-01-17T17:48:46Z

On 1/17/24 10:36 AM, Bart Van Assche wrote:
> On 1/16/24 15:34, Damien Le Moal wrote:
>> FYI, I am about to post 20-something patches that completely remove zone write
>> locking and replace it with "zone write plugging". That is done above the IO
>> scheduler and also provides zone append emulation for drives that ask for it.
>>
>> With this change:
>> - Zone append emulation is moved to the block layer, as a generic
>> implementation. sd and dm zone append emulation code is removed.
>> - Any scheduler can be used, including "none". mq-deadline zone block device
>> special support is removed.
>> - Overall, a lot less code (the series removes more code than it adds).
>> - Reordering problems such as due to IO priority is resolved as well.
>>
>> This will need a lot of testing, which we are working on. But your help with
>> testing on UFS devices will be appreciated as well.
>
> When posting this patch series, please include performance results
> (IOPS) for a zoned null_blk device instance. mq-deadline doesn't support
> more than 200 K IOPS, which is less than what UFS devices support. I
> hope that this performance bottleneck will be solved with the new
> approach.

Not really zone related, but I was very aware of the single lock
limitations when I ported deadline to blk-mq. Was always hoping that
someone would actually take the time to make it more efficient, but so
far that hasn't happened. Or maybe it'll be a case of "just do it
yourself, Jens" at some point...

--
Jens Axboe