Excessive CPU Load? FreeNAS 11.1-U4

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NASbox

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May 8, 2012
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Hi - I'm hoping one of the gurus here can tell me if this is normal, or if I've found a bug what I should do to troubleshoot.

I have an i7-3770 running FreeNAS 11.1-U4, there is nothing running on the system except:

zfs -v send SNAPSHOT | zfs recv -vd BACKUP/SNAPSHOT

Is it normal the at kernel CPU as shown by htop would be over 600%?

Prior to running the send/recv I have been repeatedly creating and destroying BACKUP, and a bunch of snapshots on BACKUP and the main pool as part of the process of testing a backup script.

If this seems like abnormal behavior, please let me know what information you want me to gather for troubleshooting.

Thanks.
 

Jailer

Not strong, but bad
Joined
Sep 12, 2014
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Post the output of top to see what's using your CPU.
 

NASbox

Guru
Joined
May 8, 2012
Messages
650
Post the output of top to see what's using your CPU.

I've attached a screen shot of htop from when I first noticed the problem.
The usage drops back to less than 0.2 when the zfs send/recv is finished.
The cpu usage is definately as a result of that operation which is why I didn't
originally post a top/htop.

I likely should add that I'm using gzip (default compression level) on
destination BACKUP pool - the source was lz4 in this case.

I don't remember if I checked CPU load, but I did some testing with gzip
on highly compressable data (public_http on web server-mostly text) and
the difference in compression was significant and the time penalty didn't
seem to be very much (on the default compression level). On max compression
the difference in CPU between default and level 9 was huge and the savings
over default weren't very much.
(I posted my test results on the forum for benefit of the community - don't know
if it's useful info in this context, but if you search my posts you should find
them very easily.)
 

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