On 7/17/20 12:44 PM, Artur Paszkiewicz wrote:
On 7/16/20 7:29 PM, Song Liu wrote:
I just noticed another issue with this work on raid456, as iostat
shows something
like:
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s
avgrq-sz avgqu-sz await r_await w_await svctm %util
nvme0n1 6306.50 18248.00 636.00 1280.00 45.11 76.19
129.65 3.03 1.23 0.67 1.51 0.76 145.50
nvme1n1 11441.50 13234.00 1069.50 961.00 71.87 55.39
128.35 3.32 1.30 0.90 1.75 0.72 146.50
nvme2n1 8280.50 16352.50 971.50 1231.00 65.53 68.65
124.77 3.20 1.17 0.69 1.54 0.64 142.00
nvme3n1 6158.50 18199.50 567.00 1453.50 39.81 76.74
118.13 3.50 1.40 0.88 1.60 0.73 146.50
md0 0.00 0.00 1436.00 1411.00 89.75 88.19
128.00 22.98 8.07 0.16 16.12 0.52 147.00
md0 here is a RAID-6 array with 4 devices. %util of > 100% is clearly
wrong here.
This only doesn't happen to RAID-0 or RAID-1 in my tests.
Artur, could you please take a look at this?
Hi Song,
I think it's not caused by this patch, because %util of the member
drives is affected as well. I reverted the patch and it's still
happening:
Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz w/s wMB/s wrqm/s %wrqm w_await wareq-sz d/s dMB/s drqm/s %drqm d_await dareq-sz f/s f_await aqu-sz %util
md0 20.00 2.50 0.00 0.00 0.00 128.00 21.00 2.62 0.00 0.00 0.00 128.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
nvme0n1 13.00 1.62 279.00 95.55 0.77 128.00 4.00 0.50 372.00 98.94 1289.00 128.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5.17 146.70
nvme1n1 15.00 1.88 310.00 95.38 0.53 128.00 21.00 2.62 341.00 94.20 1180.29 128.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 24.80 146.90
nvme2n1 16.00 2.00 310.00 95.09 0.69 128.00 19.00 2.38 341.00 94.72 832.89 128.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 15.84 146.80
nvme3n1 18.00 2.25 403.00 95.72 0.72 128.00 16.00 2.00 248.00 93.94 765.69 128.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 12.26 114.30
I was only able to reproduce it on a VM, it doesn't occur on real
hardware (for me). What was your test configuration?
Just FYI, I suspect it could be related to the commit 2b8bd423614c595
("block/diskstats: more accurate approximation of io_ticks for slow disks").
Thanks,
Guoqing
