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From Tamar Fraenkel <ta...@tok-media.com>
Subject Re: GCInspector info messages in cassandra log
Date Tue, 14 Aug 2012 15:15:51 GMT
Hi!
It helps, but before I do more actions I want to give you some more info,
and ask some questions:

*Related Info*

   1. According to my yaml file (where do I see these parameters in the jmx?
   I couldn't find them):
   in_memory_compaction_limit_in_mb: 64
   concurrent_compactors: 1, but it is commented out, so I guess it is the
   default value
   multithreaded_compaction: false
   compaction_throughput_mb_per_sec: 16
   compaction_preheat_key_cache: true
   2. According to cfstats there are the some CF with high Comacted row
   maximum sizes (1131752, 4866323 and 25109160). Others max sizes are <
   1000000. Are these considered to be problematic, what can I do to solve
   that?
   3. During compactions Cassandra is slower
   4. Running Cassandra Version 1.0.8

*Questions*
What should be the values of  in_memory_compaction_limit_in_mb
 and concurrent_compactors and how do I change them? change yaml file and
restart, or can it be done using jmx without restarting Cassandra?
What do I do about the long rows? What value is considered too big.

I appreciate your help! Thanks,



*Tamar Fraenkel *
Senior Software Engineer, TOK Media

[image: Inline image 1]

tamar@tok-media.com
Tel:   +972 2 6409736
Mob:  +972 54 8356490
Fax:   +972 2 5612956





On Tue, Aug 14, 2012 at 1:22 PM, aaron morton <aaron@thelastpickle.com>wrote:

> There are a couple of steps you can take if compaction is causing GC.
>
> - if you have a lot of wide rows consider reducing
> the in_memory_compaction_limit_in_mb yaml setting. This will slow down
> compaction but will reduce the memory usage.
>
> - reduce concurrent_compactors
>
> Both of these may slow down compaction. Once you have GC under control
> you may want to play with memory settings.
>
> Hope that helps.
>   -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 14/08/2012, at 4:45 PM, Tamar Fraenkel <tamar@tok-media.com> wrote:
>
> Hi!
> I have 3 nodes ring running on Amazon EC2.
> About once a week I see in the logs compaction messages and around the
> same time info messages about GC (see below) that I think means it is
> taking too long and happening too often.
>
> Does it mean I have to reduce my cache size?
> Thanks,
> Tamar
>
>  INFO [ScheduledTasks:1] 2012-08-13 12:50:57,593 GCInspector.java (line
> 122) GC for ParNew: 242 ms for 1 collections, 1541590352 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:27,740 GCInspector.java (line
> 122) GC for ParNew: 291 ms for 1 collections, 1458227032 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:29,741 GCInspector.java (line
> 122) GC for ParNew: 261 ms for 1 collections, 1228861368 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:30,833 GCInspector.java (line
> 122) GC for ParNew: 319 ms for 1 collections, 1120131360 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:32,863 GCInspector.java (line
> 122) GC for ParNew: 241 ms for 1 collections, 983144216 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:33,864 GCInspector.java (line
> 122) GC for ParNew: 215 ms for 1 collections, 967702720 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:34,964 GCInspector.java (line
> 122) GC for ParNew: 248 ms for 1 collections, 973803344 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:41,211 GCInspector.java (line
> 122) GC for ParNew: 265 ms for 1 collections, 1071933560 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:43,212 GCInspector.java (line
> 122) GC for ParNew: 326 ms for 1 collections, 1217367792 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:44,212 GCInspector.java (line
> 122) GC for ParNew: 245 ms for 1 collections, 1203481536 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:45,213 GCInspector.java (line
> 122) GC for ParNew: 209 ms for 1 collections, 1208819416 used; max is
> 1937768448
>  INFO [ScheduledTasks:1] 2012-08-13 12:51:46,237 GCInspector.java (line
> 122) GC for ParNew: 248 ms for 1 collections, 1338361648 used; max is
> 1937768448
>
>
>  *Tamar Fraenkel *
> Senior Software Engineer, TOK Media
>
> <tokLogo.png>
>
>
> tamar@tok-media.com
> Tel:   +972 2 6409736
> Mob:  +972 54 8356490
> Fax:   +972 2 5612956
>
>
>
>
>

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