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From Abhijit Pol <a...@rocketfuel.com>
Subject Re: Is this indicative of a GC CPU starvation?
Date Wed, 10 Nov 2010 02:16:14 GMT
how are GC settings in hbase-env.sh look like for you? did you add/remove
from out of box hbase-env.sh?

try running this on RS and watch last column, each increment should be small
sudo -u <RS_USER> jstats -gcutil <RS_PID> 1000



On Tue, Nov 9, 2010 at 10:53 AM, Stuart Smith <stu24mail@yahoo.com> wrote:

> Hello,
>
>  I just wanted to make sure that I'm interpreting a series of common issues
> correctly.
>
> I saw ZK expirations causing regionserver failures, and this in a GC log of
> one of the regionservers:
>
> 16237.033: [GC[YG occupancy: 22353 K (38336 K)]16245.298: [Rescan
> (parallel) , 0.0264040 secs]16245.325: [weak refs processing, 0.0000970
> secs] [1 CMS-remark: 1465176K(3282456K)] 1487530K(3320792K), 0.0266760 secs]
> [Times: user=0.02 sys=0.01, real=8.29 secs]
>
> 5328.127: [GC[YG occupancy: 27822 K (38336 K)]5334.773: [Rescan (parallel)
> , 0.0156270 secs]5334.788: [weak refs processing, 0.0003130 secs] [1
> CMS-remark: 1144288K(2375464K)] 1172111K(2413800K), 0.0161190 secs] [Times:
> user=0.02 sys=0.00, real=6.66 secs]
>
> I noted the rather large delta between the user/sys times & the real times
> here:
>
> [Times: user=0.02 sys=0.00, real=6.66 secs]
> [Times: user=0.02 sys=0.01, real=8.29 secs]
>
> So I'm assuming in the second of the two common causes of the GC issues?
> That is, CPU or I/O bound M/R tasks are starving the GC of CPU time?
>
> Just wanted to check that I was stringing the logic (and logs) together
> correctly.
>
> Thanks!
>
> Take care,
>  -stu
>
>
>
>

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