NETGEAR is aware of a growing number of phone and online scams. To learn how to stay safe click here.
Forum Discussion
6.6.1 Scrub Hammers CPU
And when I say hammers, I mean it runs with -1 prio and causes 6-8 kernel worker threads each vying to consume 100% of CPU. So rabid is this consumption that all other background processes, including...
It's worth noting that the resources consumed by btrfs scrub can vary widely depending on the files it's scrubbing at the time. Very fragmented files will result in a lot more I/O wait time, and more CPU consumption. Also, a ReadyNAS volume scrub also includes a MD RAID scrub, which adds to the I/O load. MD is generally pretty good at yielding to other I/O consumers, but it's still a minimum 30MB/sec used for that plus the CPU usage for parity calculation.
Still on 6.7.4.
Started scrub.
Three threads as described above, main process & two threads (shown with H command to htop)
PPID PID USER IO IORR IOWR IO PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command
1 29003 root 41462 41462 0 B3 19 -1 32180 200 16 S 5.6 0.0 0:26.28 `- btrfs scrub start /N316AR6
1 29005 root 0 0 0 B3 19 -1 32180 200 16 S 0.0 0.0 0:00.03 | `- btrfs
1 29004 root 41462 41462 0 id 19 -1 32180 200 16 D 5.6 0.0 0:26.26 | `- btrfsI'm reading that as the IO/IORR/IOWR & CPU usage is accounted for in the main process too, rather than both doing I/O & CPU.
Note active thread is idle iopriority, nice -1 (as most things spawned from readynas seem to inherit -1).
However, sort by CPU, (K command to show kernal threads), everything with CPU > 0.
PPID PID USER IO IORR IOWR IO PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command
2 29066 root 0 0 0 B4 20 0 0 0 0 R 39.9 0.0 3:52.37 kworker/u8:10
2 29043 root 0 0 0 B4 20 0 0 0 0 R 38.2 0.0 4:47.15 kworker/u8:9
2 28656 root 0 0 0 B4 20 0 0 0 0 R 37.0 0.0 4:37.22 kworker/u8:2
2 28793 root 0 0 0 B4 20 0 0 0 0 R 37.0 0.0 4:42.18 kworker/u8:3
2 30086 root 0 0 0 B4 20 0 0 0 0 R 35.8 0.0 1:05.82 kworker/u8:14
2 28903 root 57.2 57.2 0 B4 20 0 0 0 0 S 33.4 0.0 4:37.18 kworker/u8:8
2 28071 root 0 0 0 B4 20 0 0 0 0 R 33.4 0.0 4:27.62 kworker/u8:0
2 29095 root 19.2 19.2 0 B4 20 0 0 0 0 R 31.6 0.0 1:44.06 kworker/u8:13
2 28902 root 0 0 0 B4 20 0 0 0 0 R 31.0 0.0 4:56.74 kworker/u8:7
2 1515 root 0 0 0 B4 17 -1 0 0 0 R 25.6 0.0 35h04:21 md127_raid6
2 27507 root 0 0 0 B4 20 0 0 0 0 R 17.9 0.0 4:31.39 kworker/u8:1
2 29067 root 0 0 0 B4 20 0 0 0 0 R 17.9 0.0 4:30.13 kworker/u8:11
1 29003 root 45490 45490 0 B3 19 -1 32180 200 16 S 6.0 0.0 1:12.96 btrfs scrub start /N316AR6
1 29004 root 45517 45517 0 id 19 -1 32180 200 16 D 6.0 0.0 1:12.87 btrfs
2 29001 root 0 0 0 ?? 39 19 0 0 0 R 3.0 0.0 2:22.40 md127_resync
28517 28522 root 0 0 0 B4 20 0 29460 3688 3004 R 3.0 0.2 0:56.68 htop
2 1402 root 0 0 0 B0 0 -20 0 0 0 S 1.8 0.0 0:54.53 kworker/1:1H
2 1401 root 0 0 0 B0 0 -20 0 0 0 S 1.2 0.0 0:50.00 kworker/0:1H
2 1359 root 0 0 0 B0 0 -20 0 0 0 S 0.6 0.0 3:29.12 kworker/2:1H
2 1389 root 0 0 0 B0 0 -20 0 0 0 S 0.6 0.0 3:34.20 kworker/3:1H
2 7 root 0 0 0 B4 20 0 0 0 0 R 0.6 0.0 4:10.65 rcu_sched
1 3703 nut 0 0 0 B4 20 0 17240 1296 932 S 0.6 0.1 1:31.42 /lib/nut/usbhid-ups -a UPSNote all the CPU chewed up by kworker threads, Nice 0, doing little IO. (kworker IO increased later, similar numbers as above, but more threads doing IO)
btaroli's media processes (infering from the above iopriority B7/B6 - I don't know what they are doing) will have lesser nice values, and be CPU constrained. Those at B4 will have Nice 0, round-robin with all those kworker's, so ~1/12th CPU (?5/17th?).
How changing the iopriority of the other two threads can change this I can't fathom ATM.
Perhaps media threads with a 'interactive' workload should run nice -1 for now.
Longer term there should be a gap between current -1 processes (readynas etc) and default worker thread priority (currently 0 ), so intermidiate priority things can fit in the middle??
I'll repeat this on 6.7.5 when I get around to it, I'm currently juggling 10TB disks upgrading...nothing happens fast...
NETGEAR Academy
Boost your skills with the Netgear Academy - Get trained, certified and stay ahead with the latest Netgear technology!
Join Us!
