Re: [PATCH for-next v3 0/4] fixed-buffer for uring-cmd/passthrough

Jens Axboe
2022-09-04T20:45:32Z

On 9/4/22 11:01 AM, Kanchan Joshi wrote:
> On Sat, Sep 03, 2022 at 11:00:43AM -0600, Jens Axboe wrote:
>> On 9/2/22 3:25 PM, Jens Axboe wrote:
>>> On 9/2/22 1:32 PM, Jens Axboe wrote:
>>>> On 9/2/22 12:46 PM, Kanchan Joshi wrote:
>>>>> On Fri, Sep 02, 2022 at 10:32:16AM -0600, Jens Axboe wrote:
>>>>>> On 9/2/22 10:06 AM, Jens Axboe wrote:
>>>>>>> On 9/2/22 9:16 AM, Kanchan Joshi wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> Currently uring-cmd lacks the ability to leverage the pre-registered
>>>>>>>> buffers. This series adds the support in uring-cmd, and plumbs
>>>>>>>> nvme passthrough to work with it.
>>>>>>>>
>>>>>>>> Using registered-buffers showed peak-perf hike from 1.85M to 2.17M IOPS
>>>>>>>> in my setup.
>>>>>>>>
>>>>>>>> Without fixedbufs
>>>>>>>> *****************
>>>>>>>> # taskset -c 0 t/io_uring -b512 -d128 -c32 -s32 -p0 -F1 -B0 -O0 -n1 -u1 /dev/ng0n1
>>>>>>>> submitter=0, tid=5256, file=/dev/ng0n1, node=-1
>>>>>>>> polled=0, fixedbufs=0/0, register_files=1, buffered=1, QD=128
>>>>>>>> Engine=io_uring, sq_ring=128, cq_ring=128
>>>>>>>> IOPS=1.85M, BW=904MiB/s, IOS/call=32/31
>>>>>>>> IOPS=1.85M, BW=903MiB/s, IOS/call=32/32
>>>>>>>> IOPS=1.85M, BW=902MiB/s, IOS/call=32/32
>>>>>>>> ^CExiting on signal
>>>>>>>> Maximum IOPS=1.85M
>>>>>>>
>>>>>>> With the poll support queued up, I ran this one as well. tldr is:
>>>>>>>
>>>>>>> bdev (non pt)??? 122M IOPS
>>>>>>> irq driven??? 51-52M IOPS
>>>>>>> polled??????? 71M IOPS
>>>>>>> polled+fixed??? 78M IOPS
>>
>> Followup on this, since t/io_uring didn't correctly detect NUMA nodes
>> for passthrough.
>>
>> With the current tree and the patchset I just sent for iopoll and the
>> caching fix that's in the block tree, here's the final score:
>>
>> polled+fixed passthrough??? 105M IOPS
>>
>> which is getting pretty close to the bdev polled fixed path as well.
>> I think that is starting to look pretty good!
> Great! In my setup (single disk/numa-node), current kernel shows-
>
> Block MIOPS
> ***********
> command:t/io_uring -b512 -d128 -c32 -s32 -p0 -F1 -B0 -P1 -n1 /dev/nvme0n1
> plain: 1.52
> plain+fb: 1.77
> plain+poll: 2.23
> plain+fb+poll: 2.61
>
> Passthru MIOPS
> **************
> command:t/io_uring -b512 -d128 -c32 -s32 -p0 -F1 -B0 -O0 -P1 -u1 -n1 /dev/ng0n1
> plain: 1.78
> plain+fb: 2.08
> plain+poll: 2.21
> plain+fb+poll: 2.69

Interesting, here's what I have:

Block MIOPS
============
plain: 2.90
plain+fb: 3.0
plain+poll: 4.04
plain+fb+poll: 5.09

Passthru MIPS
=============
plain: 2.37
plain+fb: 2.84
plain+poll: 3.65
plain+fb+poll: 4.93

This is a gen2 optane, it maxes out at right around 5.1M IOPS. Note that
I have disabled iostats and merges generally in my runs:

echo 0 > /sys/block/nvme0n1/queue/iostats
echo 2 > /sys/block/nvme0n1/queue/nomerges

which will impact block more than passthru obviously, particularly
the nomerges. iostats should have a similar impact on both of them (but
I haven't tested either of those without those disabled).

--
Jens Axboe