[PATCHSET v2 0/5] Enable alloc caching and batched freeing for passthrough

[Anuj gupta]

On Tue, Sep 27, 2022 at 7:14 AM Jens Axboe <axboe at kernel.dk> wrote:
>
> Hi,
>
> The passthrough IO path currently doesn't do any request allocation
> batching like we do for normal IO. Wire this up through the usual
> blk_mq_alloc_request() allocation helper.
>
> Similarly, we don't currently supported batched completions for
> passthrough IO. Allow the request->end_io() handler to return back
> whether or not it retains ownership of the request. By default all
> handlers are converted to returning RQ_END_IO_NONE, which retains
> the existing behavior. But with that in place, we can tweak the
> nvme uring_cmd end_io handler to pass back ownership, and hence enable
> completion batching for passthrough requests as well.
>
> This is good for a 10% improvement for passthrough performance. For
> a non-drive limited test case, passthrough IO is now more efficient
> than the regular bdev O_DIRECT path.
>
> Changes since v1:
> - Remove spurious semicolon
> - Cleanup struct nvme_uring_cmd_pdu handling
>
> --
> Jens Axboe
>
>
I see an improvement of ~12% (2.34 to 2.63 MIOPS) with polling enabled and
an improvement of ~4% (1.84 to 1.92 MIOPS) with polling disabled using the
t/io_uring utility (in fio) in my setup with this patch series!

--
Anuj Gupta