Make IOPerDrive Configurable

[moting9]

"ioperdrive" is fixed as 4 in code, but when there are multiple disks such as 12 disks in a server, the concurrent read result is abnormal.

• this PR make "--ioperdrive" configurable by user.
• and change default value from 4 to 2.

Here is test result in Intel Xeon 8480+ with 12 pcs KIOXIA Corporation NVMe SSD Controller Cx6

./dperf -f 10GiB -i 4 /mnt/d{1..12} --verbose

┌──────────┬───────────┬───────────┬───┐
│ PATH │ READ │ WRITE │ │
│ /mnt/d10 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d5 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d1 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d6 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d7 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d9 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d2 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d11 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d3 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d4 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d8 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d12 │ 1.6 GiB/s │ 1.1 GiB/s │ ✓ │
└──────────┴───────────┴───────────┴───┘
┌───────────┬────────────┐
│ TotalREAD │ TotalWRITE │
│ 19 GiB/s │ 14 GiB/s │
└───────────┴────────────┘

./dperf -f 10GiB /mnt/d{1..12} --verbose

┌──────────┬───────────┬───────────┬───┐
│ PATH │ READ │ WRITE │ │
│ /mnt/d5 │ 2.1 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d1 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d2 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d3 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d6 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d8 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d10 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d4 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d11 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d12 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d9 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d7 │ 2.0 GiB/s │ 1.1 GiB/s │ ✓ │
└──────────┴───────────┴───────────┴───┘
┌───────────┬────────────┐
│ TotalREAD │ TotalWRITE │
│ 24 GiB/s │ 13 GiB/s │
└───────────┴────────────┘

./dperf -f 10GiB -i 1 /mnt/d{1..12} --verbose

┌──────────┬───────────┬───────────┬───┐
│ PATH │ READ │ WRITE │ │
│ /mnt/d10 │ 3.0 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d12 │ 2.9 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d4 │ 2.9 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d11 │ 2.8 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d7 │ 2.8 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d3 │ 2.8 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d1 │ 2.8 GiB/s │ 1.0 GiB/s │ ✓ │
│ /mnt/d2 │ 2.8 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d8 │ 2.8 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d6 │ 2.7 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d9 │ 2.7 GiB/s │ 1.1 GiB/s │ ✓ │
│ /mnt/d5 │ 2.7 GiB/s │ 1.1 GiB/s │ ✓ │
└──────────┴───────────┴───────────┴───┘
┌───────────┬────────────┐
│ TotalREAD │ TotalWRITE │
│ 34 GiB/s │ 13 GiB/s │
└───────────┴────────────┘

[harshavardhana]

A drive regardless of 1 thread or 4 threads should show overall performance to be the same with minor changes. Not to the extent of 1GiB/sec .

This PR however is valid for other tools not here, dperf is designed to be run once and captured. IF concurrent dperf I/O cannot be performed on the drive then there is no way it can perform for other applications.

That's why I see this to be problematic PR that can give wrong results.