[PATCH 0/4] iopoll support for io_uring/nvme passthrough

[Jens Axboe]

On 8/5/22 11:13 AM, Kanchan Joshi wrote:
> On Fri, Aug 05, 2022 at 11:04:22AM -0600, Jens Axboe wrote:
>> On 8/5/22 9:42 AM, Kanchan Joshi wrote:
>>> Hi,
>>>
>>> Series enables async polling on io_uring command, and nvme passthrough
>>> (for io-commands) is wired up to leverage that.
>>>
>>> 512b randread performance (KIOP) below:
>>>
>>> QD_batch    block    passthru    passthru-poll   block-poll
>>> 1_1          80        81          158            157
>>> 8_2         406       470          680            700
>>> 16_4        620       656          931            920
>>> 128_32      879       1056        1120            1132
>>
>> Curious on why passthru is slower than block-poll? Are we missing
>> something here?
> passthru-poll vs block-poll you mean?
> passthru does not have bio-cache, while block path is running with that.
> Maybe completion-batching is also playing some role, not too sure about that
> at the moment.

Yeah, see other email on a quick rundown. We should make
bio_map_user_iov() use the bio caching, that'd make a big difference.
Won't fully close the gap, but will be close if we exclude the lack of
fixedbufs.

-- 
Jens Axboe