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btrfs-cleaner frequently stuck at 100% CPU after 6.4.0 upgrade
Since I upgraded my RN102 to 6.4.0 last night I frequently have trouble reaching the admin interface, and my laptop has reported not being able to reach Time Machine. When I login by ssh and use ...
It seems like I found a way to get rid of the hanging btrfs-cleaner: After switching off quota
btrfs quota disable /data
btrfs-cleaner did never show up again (in top).
(After booting I usualy had about a minute to issue the command before btrfs-cleaner did spawn and prevented the command to respond.)
I did not intentionally enable quota - i guess it was enabled by default.
Good luck,
HansW
PS: Maybe the problem is known by Netgear - in their "FAQs on recently released firmware 6.4.0" (see link on top of page) they talk about "... this is likely due to the ReadyNAS performing a quota check".
Some websites also describe problems with quota and btrfs (Rockstor forum), other sites cite the quota support in btrfs as experimental (but these might be out of date).
I did not extensive testing after diabling quota that way - I'm happy that I can acces my files again ...
Hi Joachim,
Did you recently delete a very large file or a lot of files? Has there been any delete request like this or similar sent to the volume?
btrfs-cleaner is used when there is a large file(s) deletion.
Alex
Did it remove a bunch of your old snapshots? If you have snapshots and Smart Snapshot Management cleans up these snapshots, btrfs-cleaner will be busy wiping away those snapshots. In 6.4.0, we upgrade to the latest version of snapshots (which is why you can't downgrade from 6.4.0), so this could also be related.
Is there any way to turn on logging for btrfs-cleaner to find out what it's up to? As it is, I don't know why it seems to be taking longer than before since my usage profile hasn't changed that much since upgrading...
Same problem here, actually the device froze and I had to pull the plug. Nothing done lately that could cause this, just the upgrade, so perhaps listen to the guys in the posts and see what has changed in this area in your 6.4.0 release?
Just wanted to post an update to emphasise that this problem is in fact still occurring. Many times a day my NAS becomes unresponsive due to extremely high CPU usage of btrfs-cleaner.
As shown by top, btrfs-cleaner has been running for 2669 minutes (nearly 2 entire days) in a total uptime of 11 days, while readynasd has only used 75 minutes of CPU time:
top - 17:04:15 up 11 days, 18:01, 1 user, load average: 0.67, 0.65, 1.02 Tasks: 140 total, 1 running, 139 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.7 us, 4.6 sy, 0.0 ni, 51.1 id, 42.6 wa, 0.0 hi, 1.0 si, 0.0 st KiB Mem: 508804 total, 483508 used, 25296 free, 3424 buffers KiB Swap: 523708 total, 16 used, 523692 free, 369660 cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2583 root 30 10 0 0 0 S 0.0 0.0 2669:52 btrfs-cleaner 2905 root 19 -1 186m 29m 8640 S 0.3 6.0 75:54.44 readynasd 2624 messageb 20 0 4020 1356 900 S 0.0 0.3 19:35.37 dbus-daemon 404 root 20 0 0 0 0 S 0.3 0.0 6:48.03 kswapd0 7 root 20 0 0 0 0 S 0.0 0.0 5:51.99 rcu_schedThis problem did not exist before upgrading to 6.4.0 from 6.2.5. Since the upgrade, there have been no unusual activities such as deleting large amounts of files or data or removing snapshots.
There has been no response from Netgear so far regarding how to enable logging to find out why btrfs-cleaner is taking so much time or which features to disable in order to work around the problem.
I have noticed this, it happens if I manually delete a very large snapshot.
James
Hi Alex,
most of the data traffic on my RN102 is from TimeMachine on a couple of macs, but the load hasn't changed since before the update.
I'm still getting very high load from btrfs-cleaner several times a day, so much so that TimeMachine gives an error message saying the backup disk isn't available. The CPU time after 6 days is now up to a record 1270 minutes for btrfs-cleaner with readynasd at a mere 36 minutes, according to "top".
Joachim
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