manwe_
l33t
Joined: 01 Feb 2006
Posts: 650
Location: Universe
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 Posted: Mon Feb 12, 2018 9:08 pm Post subject: ioping weirdness with nvme disk |
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Hi *.
Maybe you can explain this, I'm out of ideas:
First launch:
| Code: | # ioping /dev/nvme0n1
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=1 time=5.62 ms (warmup)
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=2 time=5.72 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=3 time=5.59 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=4 time=5.61 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=5 time=5.75 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=6 time=5.57 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=7 time=5.77 ms (slow)
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=8 time=5.66 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=9 time=5.58 ms (fast)
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=10 time=5.73 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=11 time=5.70 ms
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=12 time=5.63 ms
^C
--- /dev/nvme0n1 (block device 232.9 GiB) ioping statistics ---
11 requests completed in 62.3 ms, 44 KiB read, 176 iops, 706.2 KiB/s
generated 12 requests in 11.6 s, 48 KiB, 1 iops, 4.13 KiB/s
min/avg/max/mdev = 5.57 ms / 5.66 ms / 5.77 ms / 69.4 us
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Second launch:
| Code: | # ioping /dev/nvme0n1
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=1 time=103.3 us (warmup)
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=2 time=43.7 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=3 time=92.7 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=4 time=35.1 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=5 time=29.3 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=6 time=97.5 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=7 time=91.4 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=8 time=107.7 us (slow)
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=9 time=93.7 us
4 KiB <<< /dev/nvme0n1 (block device 232.9 GiB): request=10 time=118.1 us (slow)
^C
--- /dev/nvme0n1 (block device 232.9 GiB) ioping statistics ---
9 requests completed in 709.2 us, 36 KiB read, 12.7 k iops, 49.6 MiB/s
generated 10 requests in 9.39 s, 40 KiB, 1 iops, 4.26 KiB/s
min/avg/max/mdev = 29.3 us / 78.8 us / 118.1 us / 31.4 us
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Over 70 times slower with first launch (5.66 ms vs 78.8 us). What changed you ask? Duing second launch there was dd writing to the disk simultaneously with rate 100MBps.
| Code: | | pv -L 100M /dev/zero | dd of=zero bs=5M |
How the hell ping is 70 times faster when disk is writing stuff then when it's idle? |
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