Re: [PATCH 0/5] brd: Allow to change block sizes

[Pankaj Raghav <p.raghav@samsung.com>]

Hi Hannes,

On Mon, Mar 06, 2023 at 01:01:22PM +0100, Hannes Reinecke wrote:
> Hi all,
> 
> meat to the bone: with this patchset one can change the physical and
> logical block size of the 'brd' ramdisk driver.
> Default is 512 (for both); one can easily increase the physical block
> size to 16k and the logical block size to 4k.
> Increasing the logcial block size beyond 4k gives some 'interesting'
> crashes.

I did something similar for an internal prototype to test large block
size. I ran the perf test suite I created on your changes and I can
clearly see a perf increase for large block IOs.

I enabled huge pages and used the iomem=mmaphuge option in fio to test
large block IOs. Here are my results:

base: next-20230307
new: base with your changes on top

bw: bandwith in MiB/s

For each set of rd_blksize and rd_logical_blksize, I ran the test with
different fio blocksize as indicated by `io_uring_iod_128_bs_4k`

rd_blksize=8192 and rd_logical_blksize=4096
+------------------------+-------------+------------+-------+----------+---------+-------+
| io_uring_iod_128_bs_4k | base[kiops] | new[kiops] | delta | base[bw] | new[bw] | delta |
+------------------------+-------------+------------+-------+----------+---------+-------+
|          read          |     567     |    605     |  6.7  |   2214   |  2362   | 6.68  |
|        randread        |     517     |    529     | 2.32  |   2019   |  2066   | 2.33  |
|         write          |     551     |    558     | 1.27  |   2154   |  2179   | 1.16  |
|       randwrite        |     481     |    502     | 4.37  |   1880   |  1962   | 4.36  |
+------------------------+-------------+------------+-------+----------+---------+-------+
+------------------------+-------------+------------+-------+----------+---------+-------+
| io_uring_iod_128_bs_8k | base[kiops] | new[kiops] | delta | base[bw] | new[bw] | delta |
+------------------------+-------------+------------+-------+----------+---------+-------+
|          read          |     462     |    512     | 10.82 |   3611   |  3997   | 10.69 |
|        randread        |     426     |    445     | 4.46  |   3326   |  3480   | 4.63  |
|         write          |     442     |    472     | 6.79  |   3454   |  3687   | 6.75  |
|       randwrite        |     401     |    426     | 6.23  |   3134   |  3328   | 6.19  |
+------------------------+-------------+------------+-------+----------+---------+-------+
+-------------------------+-------------+------------+-------+----------+---------+-------+
| io_uring_iod_128_bs_16k | base[kiops] | new[kiops] | delta | base[bw] | new[bw] | delta |
+-------------------------+-------------+------------+-------+----------+---------+-------+
|          read           |     343     |    390     | 13.7  |   5360   |  6086   | 13.54 |
|        randread         |     317     |    364     | 14.83 |   4946   |  5694   | 15.12 |
|          write          |     335     |    346     | 3.28  |   5235   |  5414   | 3.42  |
|        randwrite        |     305     |    327     | 7.21  |   4759   |  5106   | 7.29  |
+-------------------------+-------------+------------+-------+----------+---------+-------+

rd_blksize=16384 and rd_logical_blksize=4096
+------------------------+-------------+------------+-------+----------+---------+-------+
| io_uring_iod_128_bs_4k | base[kiops] | new[kiops] | delta | base[bw] | new[bw] | delta |
+------------------------+-------------+------------+-------+----------+---------+-------+
|          read          |     576     |    586     | 1.74  |   2250   |  2291   | 1.82  |
|        randread        |     524     |    548     | 4.58  |   2046   |  2139   | 4.55  |
|         write          |     533     |    545     | 2.25  |   2081   |  2129   | 2.31  |
|       randwrite        |     484     |    496     | 2.48  |   1892   |  1938   | 2.43  |
+------------------------+-------------+------------+-------+----------+---------+-------+
+------------------------+-------------+------------+-------+----------+---------+-------+
| io_uring_iod_128_bs_8k | base[kiops] | new[kiops] | delta | base[bw] | new[bw] | delta |
+------------------------+-------------+------------+-------+----------+---------+-------+
|          read          |     461     |    491     | 6.51  |   3601   |  3836   | 6.53  |
|        randread        |     425     |    472     | 11.06 |   3323   |  3684   | 10.86 |
|         write          |     454     |    465     | 2.42  |   3543   |  3632   | 2.51  |
|       randwrite        |     395     |    430     | 8.86  |   3086   |  3357   | 8.78  |
+------------------------+-------------+------------+-------+----------+---------+-------+
+-------------------------+-------------+------------+-------+----------+---------+-------+
| io_uring_iod_128_bs_16k | base[kiops] | new[kiops] | delta | base[bw] | new[bw] | delta |
+-------------------------+-------------+------------+-------+----------+---------+-------+
|          read           |     338     |    400     | 18.34 |   5282   |  6255   | 18.42 |
|        randread         |     317     |    384     | 21.14 |   4959   |  5997   | 20.93 |
|          write          |     335     |    354     | 5.67  |   5239   |  5525   | 5.46  |
|        randwrite        |     303     |    326     | 7.59  |   4728   |  5097   |  7.8  |
+-------------------------+-------------+------------+-------+----------+---------+-------+