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From Ara Ebrahimi <ara.ebrah...@argyledata.com>
Subject Re: hdfs cpu usage
Date Sun, 08 Feb 2015 01:34:23 GMT
Hi,

On all nodes. Nope, this is the behavior we’ve been seeing since we started testing a few
weeks ago. Yes the behavior persists after restarts.

Ara.

On Feb 7, 2015, at 10:50 AM, Keith Turner <keith@deenlo.com<mailto:keith@deenlo.com>>
wrote:

Is this happening on just one node, or all nodes?  Have you run w/o problem on google cloud
env before?  Do you see the problem if you restart the vms?

On Fri, Feb 6, 2015 at 9:34 PM, Ara Ebrahimi <ara.ebrahimi@argyledata.com<mailto:ara.ebrahimi@argyledata.com>>
wrote:
Hi,

We’re seeing some weird behavior from the hdfs daemon on google cloud environment when we
use accumulo Scanner to sequentially scan a table. Top reports 200-300% cpu usage for the
hdfs daemon. Accumulo is also around 500%. iostat %util is low. avgrq-sz is low, rMB/s is
low, there’s lots of free memory. It seems like something causes the hdfs daemon to consume
a lot of cpu and not to send enough read requests to the disk (ssd actually, so disk is super
fast and vastly under-utilized). The process which sends scan requests to accumulo is 500%
active (using 3 query batch threads and aggressive scan-batch-size/read-ahead-threashold values).
So it seems like somehow hdfs is the bottleneck. On another cluster we rarely see hdfs daemon
going over 10% cpu usage. Any idea what the issue could be?

Thanks,
Ara.



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