Our experience shows that write load (memtables) impacts ParNew GC most. More writes, more frequent ParNew GC. Time of ParNew GC depends on how many writes was made during cycle between ParNew GC's and size of NEW_HEAP (young gen).
Basicly ParNew GC itself takes longer when more objects have to be copied from young to old space. So reads and compactions will not promote objects to old space (short living objects) and you can see that increased reads and compactions during the same write load will increase GC frequency but decrease GC pause time. Best regards / Pagarbiai Viktor Jevdokimov Senior Developer Email: viktor.jevdoki...@adform.com<mailto:viktor.jevdoki...@adform.com> Phone: +370 5 212 3063, Fax +370 5 261 0453 J. Jasinskio 16C, LT-01112 Vilnius, Lithuania Follow us on Twitter: @adforminsider<http://twitter.com/#!/adforminsider> Take a ride with Adform's Rich Media Suite<http://vimeo.com/adform/richmedia> [Adform News] <http://www.adform.com> [Adform awarded the Best Employer 2012] <http://www.adform.com/site/blog/adform/adform-takes-top-spot-in-best-employer-survey/> Disclaimer: The information contained in this message and attachments is intended solely for the attention and use of the named addressee and may be confidential. If you are not the intended recipient, you are reminded that the information remains the property of the sender. You must not use, disclose, distribute, copy, print or rely on this e-mail. If you have received this message in error, please contact the sender immediately and irrevocably delete this message and any copies. From: Ananth Gundabattula [mailto:agundabatt...@threatmetrix.com] Sent: Tuesday, June 18, 2013 10:31 AM To: user@cassandra.apache.org Subject: What is the effect of reducing the thrift message sizes on GC We are currently running on 1.1.10 and planning to migrate to a higher version 1.2.4. The question pertains to tweaking all the knobs to reduce GC related issues ( we have been fighting a lot of really bad GC issues on 1.1.10 and met with little success all the way using 1.1.10) Taking into consideration GC tuning is a black art, I was wondering if we can have some good effect on the GC by tweaking the following settings: *thrift_framed_transport_size_in_mb & thrift_max_message_length_in_mb* * * Our system is a very short column (both in number of columns and data sizes ) tables but having millions/billions of rows in each column family. The typical number of columns in each column family is 4. The typical lookup involves specifying the row key and fetching one column most of the times. The writes are also similar except for one keyspace where the number of columns are 50 but very small data sizes per column. Assuming we can tweak the config values : * * * > thrift_framed_transport_size_in_mb & * * > thrift_max_message_length_in_mb * to lower values in the above context, I was wondering if it helps in the GC being invoked less if the thrift settings reflect our data model reads and writes ? For example: What is the impact by reducing the above config values on the GC to say 1 mb rather than say 15 or 16 ? Thanks a lot for your inputs and thoughts. Regards, Ananth
<<inline: signature-logo2eb9.png>>
<<inline: signature-best-employer-logo7ec4.png>>
