Re: [PATCH v4 0/8] implement async block discards and other ops via io_uring

[Jens Axboe <axboe@kernel.dk>]

On 9/6/24 4:57 PM, Pavel Begunkov wrote:
> There is an interest in having asynchronous block operations like
> discard and write zeroes. The series implements that as io_uring commands,
> which is an io_uring request type allowing to implement custom file
> specific operations.
> 
> First 4 are preparation patches. Patch 5 introduces the main chunk of
> cmd infrastructure and discard commands. Patches 6-8 implement
> write zeroes variants.

Sitting in for-6.12/io_uring-discard for now, as there's a hidden
dependency with the end/len patch in for-6.12/block.

Ran a quick test - have 64 4k discards inflight. Here's the current
performance, with 64 threads with sync discard:

qd64 sync discard: 21K IOPS, lat avg 3 msec (max 21 msec)

and using io_uring with async discard, otherwise same test case:

qd64 async discard: 76K IOPS, lat avg 845 usec (max 2.2 msec)

If we switch to doing 1M discards, then we get:

qd64 sync discard: 14K IOPS, lat avg 5 msec (max 25 msec)

and using io_uring with async discard, otherwise same test case:

qd64 async discard: 56K IOPS, lat avg 1153 usec (max 3.6 msec)

This is on a:

Samsung Electronics Co Ltd NVMe SSD Controller PM174X

nvme device. It doesn't have the fastest discard, but still nicely shows
the improvement over a purely sync discard.

-- 
Jens Axboe